Delay line, a delay locked loop circuit and a semiconductor apparatus using the delay line and the delay locked loop circuit

ABSTRACT

A delay locked loop circuit includes a first delay locked loop and a second delay locked loop having different characteristics. The first delay locked loop performs a delay-locking operation on a reference clock signal to generate a delay locked clock signal. The second delay locked loop performs a delay-locking operation on the delay locked clock signal to generate an internal clock signal.

CROSS-REFERENCES TO RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 16/911,888, filed on Jun. 25, 2020, and claimspriority under 35 U.S.C. § 119(a) to Korean application numbers10-2019-0110563 and 10-2019-0110569, filed on Sep. 6, 2019, in theKorean Intellectual Property Office, which is incorporated herein byreference in its entirety as set forth in full.

BACKGROUND 1. Technical Field

Various embodiments generally relate to an integrated circuittechnology, and more particularly, to a delay line, a delay locked loopcircuit and a semiconductor apparatus using the delay line and delaylocked loop.

2. Related Art

An electronic device includes a lot of electronic elements and, acomputer system may include a lot of semiconductor apparatuses eachconfigured by a semiconductor. Semiconductor apparatuses configuring acomputer system may communicate with one another by transmitting andreceiving a clock signal and data. The semiconductor apparatus mayoperate in synchronization with a clock signal. The semiconductorapparatus may transmit and/or receive a system clock signal to and/orfrom an external apparatus (i.e., another semiconductor apparatus) andmay transmit and/or receive data to and/or from the external apparatusin synchronization with the system clock signal. The semiconductorapparatus may include a clock buffer and/or a receiver to receive thesystem clock signal and may transfer the received system clock signal toan internal circuit related to data input/output operation and aninternal circuit operative in synchronization with a clock signal.Therefore, there may occur phase difference between the system clocksignal and the clock signal, which the internal circuits receive, due todelay time occurring within the semiconductor apparatus. Therefore, thesemiconductor apparatus includes a delay locked loop circuit tocompensate for the above-described phase difference. In general,examples of the delay locked loop circuit are a digital delay lockedloop utilizing a digitally controlled delay line and an analog delaylocked loop utilizing a voltage-controlled delay line.

SUMMARY

In accordance with an embodiment, a delay locked loop circuit mayinclude a first delay locked loop and a second delay locked loop. Thefirst delay locked loop may perform a delay-locking operation on thereference clock signal based on a reference clock signal and an internalclock signal to generate a delay locked clock signal. The second delaylocked loop may perform a delay-locking operation on the delay lockedclock signal based on the delay locked clock signal and the internalclock signal to generate the internal clock signal.

In accordance with an embodiment, a semiconductor apparatus may includea clock receiver, a division circuit, a first delay locked loop, asecond delay locked loop and a clock generation circuit. The clockreceiver may buffer an external clock signal to output a buffered clocksignal. The division circuit may divide the buffered clock signal togenerate a reference clock signal and selectively output the bufferedclock signal based on a frequency information signal. The first delaylocked loop may perform a delay-locking operation based on the referenceclock signal and one signal selected on the basis of the frequencyinformation signal between a first output clock signal and a secondoutput clock signal to generate a first delay locked clock signal fromthe reference clock signal and a second delay locked clock signal fromthe buffered clock signal. The second delay locked loop may perform adelay-locking operation on the first delay locked clock signal based onthe first delay locked clock signal and the first output clock signal togenerate the first output clock signal. The clock generation circuit maygenerate the second output clock signal based on the second delay lockedclock signal.

In accordance with an embodiment, a delay locked loop circuit mayinclude a voltage-controlled delay line, a calibration circuit, a phasedetector and a charge pump. The voltage-controlled delay line may delaya reference clock signal based on a delay control voltage to generate aninternal clock signal and a feedback clock signal. The calibrationcircuit may delay the internal clock signal and the feedback clocksignal based on the internal clock signal and the feedback clock signalto generate a delayed reference clock signal and a delayed feedbackclock signal. The phase detector configured to compare phases betweenthe delayed reference clock signal and the delayed feedback clock signalto generate a phase detection signal. The charge pump may generate thedelay control voltage based on the phase detection signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a semiconductorapparatus in accordance with an embodiment;

FIG. 2 is a diagram illustrating a configuration of a delay locked loopcircuit in accordance with an embodiment;

FIG. 3 is a diagram schematically illustrating configurations of asecond phase detector and a charge pump illustrated in FIG. 2 ;

FIG. 4 is a diagram illustrating a configuration of an analog delaylocked loop in accordance with an embodiment;

FIG. 5 is a diagram illustrating a configuration of a timing skewdetector illustrated in FIG. 4 ;

FIG. 6 is a diagram illustrating a configuration of a delay adjusterillustrated in FIG. 4 ;

FIG. 7 is a timing diagram illustrating operations of a calibrationcircuit and an analog delay locked loop in accordance with anembodiment;

FIG. 8A is a diagram illustrating a configuration of a delay line inaccordance with an embodiment;

FIG. 8B is a timing diagram illustrating an operation of the delay lineillustrated in FIG. 8A;

FIG. 9A is a diagram illustrating a configuration of a delay line inaccordance with an embodiment;

FIG. 9B is a timing diagram illustrating an operation of the delay lineillustrated in FIG. 9A;

FIGS. 10A, 10B, and 10C are diagrams illustrating configurations ofdelay lines in accordance with an embodiment; and

FIG. 11 is a diagram illustrating a configuration of a semiconductorapparatus in accordance with an embodiment.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating a configuration of a semiconductorapparatus 100 in accordance with an embodiment. Referring to FIG. 1 ,the semiconductor apparatus 100 may receive a clock signal CLK togenerate a plurality of internal clock signals. The clock signal CLK maybe an external clock signal provided from an external apparatus coupledto the semiconductor apparatus 100. In an embodiment, the clock signalCLK may be a periodic signal generated from a clock generator such as anoscillator. The semiconductor apparatus 100 may perform a delay-lockingoperation on the clock signal CLK to generate the plurality of internalclock signals. The semiconductor apparatus 100 may include a delaylocked loop circuit including at least two delay locked loops, whichhave different characteristics from each other. The delay locked loopcircuit may perform the delay-locking operation on the clock signal CLKthrough at least one between the two delay locked loops. The two delaylocked loops may include a digital delay locked loop and an analog delaylocked loop.

The semiconductor apparatus 100 may include a clock receiver 110 and adelay locked loop circuit 120. The clock receiver 110 may receive theclock signal CLK. The clock receiver 110 may receive the clock signalCLK to output a buffered clock signal CLKR. The clock signal CLK may betransmitted, together with a complementary signal CLKB, as adifferential signal. The clock signal CLK may be transmitted as asingle-ended signal. When the clock signal CLK is transmitted as adifferential signal, the clock receiver 110 may differentially amplifythe clock signal CLK and the complementary signal CLKB to output thebuffered clock signal CLKR. When the clock signal CLK is transmitted asa single-ended signal, the clock receiver 110 may differentially amplifythe clock signal CLK and a reference voltage VREF to output the bufferedclock signal CLKR. The reference voltage VREF may have a voltage levelcorresponding to a middle of the amplitude of the clock signal CLK.

The delay locked loop circuit 120 may receive a reference clock signaland may perform a delay-locking operation on the reference clock signal.The buffered clock signal CLKR generated from the clock receiver 110 maybe provided as the reference clock signal. The semiconductor apparatus100 may further include division circuit 130. The division circuit 130may receive the buffered clock signal CLKR and may divide the frequencyof the buffered clock signal CLKR to provide the divided clock signal asthe reference clock signal. When the semiconductor apparatus 100operates at a relatively low frequency, the delay locked loop circuit120 may receive the buffered clock signal CLKR as the reference clocksignal to perform a delay-locking operation. When the semiconductorapparatus 100 operates at a relatively high frequency, the delay lockedloop circuit 120 may receive the clock signal, which is divided by thedivision circuit 130, as the reference clock signal to perform adelay-locking operation. The division circuit 130 may divide thebuffered clock signal CLKR to generate a first divided clock signalICLK, a second divided clock signal QCLK, a third divided clock signalIBCLK and a fourth divided clock signal QBCLK.

The first to fourth divided clock signals ICLK, QCLK, IBCLK and QBCLKmay have lower frequencies or longer periods than the buffered clocksignal CLKR. The first divided clock signal ICLK may have the same phaseas the buffered clock signal CLKR and may have a leading phase to thesecond divided clock signal QCLK by an amount of 90 degrees. The seconddivided clock signal QCLK may have a leading phase to the third dividedclock signal IBCLK by an amount of 90 degrees. The third divided clocksignal IBCLK may have a leading phase to the fourth divided clock signalQBCLK by an amount of 90 degrees. The fourth divided clock signal QBCLKmay have a leading phase to the first divided clock signal ICLK by anamount of 90 degrees. The delay locked loop circuit 120 may receive thefirst divided clock signal ICLK as the reference clock signal and mayperform a delay-locking operation on the first divided clock signalICLK. In an embodiment, the delay locked loop circuit 120 may receivethe second divided clock signal QCLK as the reference clock signal andmay perform a delay-locking operation on the second divided clock signalQCLK.

The delay locked loop circuit 120 may include a first delay locked loop121 and a second delay locked loop 122. The first delay locked loop 121may be a digital delay locked loop. The second delay locked loop 122 maybe an analog delay locked loop. The first delay locked loop 121 mayreceive the reference clock signal and an internal reference clocksignal. The first delay locked loop 121 may perform a delay-lockingoperation on the reference clock signal based on the reference clocksignal and the internal reference clock signal to generate a delaylocked clock signal CLKDLL. The second delay locked loop 122 may receivethe delay locked clock signal CLKDLL and the internal reference clocksignal. The second delay locked loop 122 may receive the delay lockedclock signal CLKDLL and the internal reference clock signal and mayperform a delay-locking operation on the delay locked clock signalCLKDLL to generate the internal reference clock signal.

For compensation for modelled delay time, the first delay locked loop121 may delay the reference clock signal to generate the delay lockedclock signal CLKDLL. The second delay locked loop 122 may adjust thephase of the delay locked clock signal CLKDLL and may generate, from thedelay locked clock signal CLKDLL, a plurality of internal clock signalshaving different phases from one another. The plurality of internalclock signals may include a first internal clock signal ICLKD, a secondinternal clock signal QCLKD, a third internal clock signal IBCLKD and afourth internal clock signal QBCLKD. The first internal clock signalICLKD may be provided as the internal reference clock signal. The firstinternal clock signal ICLKD may have a leading phase to the secondinternal clock signal QCLKD by an amount of 90 degrees. The secondinternal clock signal QCLKD may have a leading phase to the thirdinternal clock signal IBCLKD by an amount of 90 degrees. The thirdinternal clock signal IBCLKD may have a leading phase to the fourthinternal clock signal QBCLKD by an amount of 90 degrees. The fourthinternal clock signal QBCLKD may have a leading phase to the firstinternal clock signal ICLKD by an amount of 90 degrees. The first tofourth internal clock signals ICLKD, QCLKD, IBCLKD and QBCLKD may beprovided to internal circuits, which operate in synchronization with aclock signal among various internal circuits included in thesemiconductor apparatus 100. Hereinafter, the terms “internal referenceclock signal” and “internal clock signal” may indicate the same clocksignal unless explicitly stated otherwise.

In general, a digital delay locked loop may be capable of performing afast delay-locking operation and may perform a delay-locking operationon a clock signal having a broader frequency band than an analog delaylocked loop. However, it may be difficult for a delay locked loop withone delay line to perform a delay-locking operation on a clock signalhaving a particular frequency or higher. A dual delay locked loop isdesigned to have two delay lines in order to settle the difficulty.However, there may easily occur a skew on phases of a plurality ofinternal clock signals generated from the dual delay locked loop due toprocess variation between the two delay lines. Therefore, in accordancewith an embodiment, the semiconductor apparatus 100 adopts the delaylocked loop circuit 120 having both of a digital delay locked loop andan analog delay locked loop, which makes it possible to perform adelay-locking operation on a clock signal having a high frequency and togenerate a plurality of internal clock signals having precise phasedifference.

FIG. 2 is a diagram illustrating a configuration of a delay locked loopcircuit 200 in accordance with an embodiment. The delay locked loopcircuit 200 may be applied as the delay locked loop circuit 120illustrated in FIG. 1 . Referring to FIG. 2 , the delay locked loopcircuit 200 may include a first delay locked loop 210 and a second delaylocked loop 220. The first delay locked loop 210 may be a digital delaylocked loop. The second delay locked loop 220 may be an analog delaylocked loop. The first delay locked loop 210 may receive a referenceclock signal REFCLK and an internal clock signal ICLKD. The first delaylocked loop 210 may perform a delay-locking operation on the referenceclock signal REFCLK based on the reference clock signal REFCLK and theinternal clock signal ICLKD to generate a delay locked clock signalCLKDLL. The second delay locked loop 220 may receive the delay lockedclock signal CLKDLL. The second delay locked loop 220 may perform adelay-locking operation on the delay locked clock signal CLKDLL togenerate first to fourth internal clock signals ICLKD, QCLKD, IBCLKD andQBCLKD. Any one among the first to fourth internal clock signals ICLKD,QCLKD, IBCLKD and QBCLKD may be provided as the internal reference clocksignal. For example, the first internal clock signal ICLKD may beutilized as the internal reference clock signal.

The first delay locked loop 210 may include a first delay line 211, areplica 212, a first phase detector 213 and a delay controller 214. Thefirst delay line 211 may receive the reference clock signal REFCLK and adelay control signal DC. The first delay line 211 may delay thereference clock signal REFCLK based on the delay control signal DC togenerate the delay locked clock signal CLKDLL. The first delay line 211may be a digitally controlled delay line. A delay amount of the firstdelay line 211 may be set on the basis of the delay control signal DC.The first delay line 211 may delay the reference clock signal REFCLK bythe delay amount, which is set by the delay control signal DC, togenerate the delay locked clock signal CLKDLL.

The replica 212 may receive the internal clock signal ICLKD as theinternal reference clock signal. The replica 212 may delay the internalclock signal ICLKD to generate a first feedback clock signal FBCLK1. Thereplica 212 may be designed by modelling a transmission path, throughwhich the clock signal CLK is transferred within the semiconductorapparatus 100 illustrated in FIG. 1 . Therefore, the replica 212 mayhave a delay amount corresponding to delay time occurring due to thetransmission path, through which the clock signal CLK is transferred.The replica 212 may delay the internal reference clock signal by anamount of the modelled delay time to generate the first feedback clocksignal FBCLK1.

The first phase detector 213 may receive the reference clock signalREFCLK and the first feedback clock signal FBCLK1. The first phasedetector 213 may compare phases between the reference clock signalREFCLK and the first feedback clock signal FBCLK1 to generate a firstphase detection signal PD1. The first phase detector 213 may change thelogic level of the first phase detection signal PD1 depending on whetherthe reference clock signal REFCLK has a leading phase or a lagging phaseto the first feedback clock signal FBCLK1. For example, the first phasedetector 213 may generate, when the reference clock signal REFCLK has aleading phase to the first feedback clock signal FBCLK1, the first phasedetection signal PD1 having a logic high level. For example, the firstphase detector 213 may generate, when the reference clock signal REFCLKhas a lagging phase to the first feedback clock signal FBCLK1, the firstphase detection signal PD1 having a logic low level.

The delay controller 214 may receive the first phase detection signalPD1 to generate the delay control signal DC. The delay control signal DCmay be a digital code signal having a plurality of bits. The delaycontroller 214 may change a code value of the delay control signal DCbased on the first phase detection signal PD1. A delay amount of thefirst delay line 211 may increase or decrease depending on the codevalue of the delay control signal DC. The first delay locked loop 210may perform a delay-locking operation by changing the code value of thedelay control signal DC until the reference clock signal REFCLK and thefirst feedback clock signal FBCLK1 have the same phase. The first delaylocked loop 210 may be locked by fixing and/or maintaining the codevalue of the delay control signal DC when the reference clock signalREFCLK and the first feedback clock signal FBCLK1 have the same phase.In an embodiment, the first delay locked loop 210 may generate the delaylocked clock signal CLKDLL by performing a delay-locking operation onthe reference clock signal REFCLK to set a delay of the reference clocksignal REFCLK when a first feedback clock signal FBCLK1 has the samephase as the reference clock signal REFCLK.

The second delay locked loop 220 may include a second delay line 221, asecond phase detector 222 and a charge pump 223. The second delay line221 may receive the delay locked clock signal CLKDLL output from thefirst delay locked loop 210. The second delay line 221 may receive adelay control voltage VC and may delay the delay locked clock signalCLKDLL based on the delay control voltage VC to generate a plurality ofdelayed clock signals. The second delay line 221 may be avoltage-controlled delay line. A delay amount of the second delay line221 may be set on the basis of the delay control voltage VC, which is ananalog signal. The second delay line 221 may delay the delay lockedclock signal CLKDLL by the delay amount, which is set by the delaycontrol voltage VC, to generate the plurality of delayed clock signals.The second delay line 221 may output, as the first to fourth internalclock signals ICLKD, QCLKD, IBCLKD and QBCLKD, four among the pluralityof delayed clock signals and may output, as a second feedback clocksignal FBCLK2, another one among the plurality of delayed clock signals.

The second delay line 221 may include a plurality of delay cells.Although FIG. 2 exemplifies the second delay line 221 having nine delaycells DC1, DC2, DC3, DC4, DC5, DC6, DC7, DC8 and DC9, an embodiment willnot be limited thereto. The number of delay cells included in the seconddelay line 221 may be greater or less than nine. Referring to FIGS. 1and 2 , one delay cell may be set to have delay time corresponding to aquarter of the period of the clock signal CLK. When any one between thefirst divided clock signal ICLK and the second divided clock signal QCLKoutput from the division circuit 130 is provided as the reference clocksignal REFCLK, the one delay cell may be set to have delay timecorresponding to an eighth of the period of the reference clock signalREFCLK. The second delay line 221 may provide, as the first internalclock signal ICLKD, a delayed clock signal output from the first delaycell DC1. The first internal clock signal ICLKD may be provided as theinternal reference clock signal. The second delay line 221 may provide,as the second internal clock signal QCLKD, a delayed clock signal outputfrom the third delay cell DC3. The second delay line 221 may provide, asthe third internal clock signal IBCLKD, a delayed clock signal outputfrom the fifth delay cell DC5. The second delay line 221 may provide, asthe fourth internal clock signal QBCLKD, a delayed clock signal outputfrom the seventh delay cell DC7. The second delay line 221 may provide,as the second feedback clock signal FBCLK2, a delayed clock signaloutput from the last delay cell DC9.

The second phase detector 222 may receive the internal reference clocksignal and the second feedback clock signal FBCLK2. The second phasedetector 222 may generate a second phase detection signal PD2 based onthe phases of the internal clock signal ICLKD, which is provided as theinternal reference clock signal, and the second feedback clock signalFBCLK2. For example, the second phase detection signal PD2 may includean up signal UP and a down signal DN. The second phase detector 222 mayenable the up signal UP based on the phase of the internal clock signalICLKD. The second phase detector 222 may enable the down signal DN basedon the phase of the second feedback clock signal FBCLK2. The secondphase detector 222 may enable the up signal UP when the phase of theinternal clock signal ICLKD transitions from a logic low level to alogic high level. The second phase detector 222 may enable the downsignal DN when the phase of the second feedback clock signal FBCLK2transitions from a logic low level to a logic high level. The secondphase detector 222 may reset the up signal UP and the down signal DNwhen a predetermined time elapses. The second phase detector 222 maydisable both of the up signal UP and the down signal DN when thepredetermined time elapses from a time point, at which any signal isenabled later than the other signal between the up signal UP and thedown signal DN. The predetermined time may be less than a timecorresponding to a half of the period of the reference clock signalREFCLK and/or the second feedback clock signal FBCLK2. The word“predetermined” as used herein with respect to a parameter, such as apredetermined time and predetermined amount, means that a value for theparameter is determined prior to the parameter being used in a processor algorithm. For some embodiments, the value for the parameter isdetermined before the process or algorithm begins. In other embodiments,the value for the parameter is determined during the process oralgorithm but before the parameter is used in the process or algorithm.

The charge pump 223 may receive the second phase detection signal PD2and may generate the delay control voltage VC based on the second phasedetection signal PD2. The charge pump 223 may raise the voltage level ofthe delay control voltage VC based on the up signal UP and may lower thevoltage level of the delay control voltage VC based on the down signalDN. When the voltage level of the delay control voltage VC rises, thedelay time of the delay cells DC1 to DC9 configuring the second phasedetector 222 may decrease. When the voltage level of the delay controlvoltage VC lowers, the delay time of the delay cells DC1 to DC9configuring the second phase detector 222 may increase. The second delaylocked loop 220 may perform a delay-locking operation by changing thevalue of the delay control voltage VC until the internal reference clocksignal and the second feedback clock signal FBCLK2 have the same phase.The second delay locked loop 220 may be locked by fixing and maintainingthe voltage level of the delay control voltage VC when the internalreference clock signal and the second feedback clock signal FBCLK2 havethe same phase. In an embodiment, the second delay locked loop 220 maygenerate the internal reference clock signal by performing adelay-locking operation on the delay locked clock signal CLKDLL to set adelay of the delay locked clock signal CLKDLL when a second feedbackclock signal FBCLK2 has the same phase as the internal reference clocksignal.

FIG. 3 is a diagram schematically illustrating configurations of thesecond phase detector 222 and the charge pump 223 illustrated in FIG. 2. The second phase detector 222 may include a first set of pluraldrivers 311 and a second set of plural drivers 312. The first set ofplural drivers 311 may receive the first internal clock signal ICLKD andmay generate the up signal UP by driving the first internal clock signalICLKD. The second set of plural drivers 312 may receive the secondfeedback clock signal FBCLK2 and may generate the down signal DN bydriving the second feedback clock signal FBCLK2.

The charge pump 223 may include a pull-up current source 321, apull-down current source 322, a capacitor 323, a first switch 324 and asecond switch 325. The pull-up current source 321 may be coupled betweena node, from which a high voltage VH is provided, and an output node ON.The pull-up current source 321 may generate a pull-up current IUP. Thedelay control voltage VC may be generated from the output node ON. Thepull-up current source 321 may be implemented by at least one P-channelMOS transistor configured to receive a bias voltage or a current controlsignal. The pull-down current source 322 may be coupled between theoutput node ON and a node, from which a low voltage VL is provided. Thepull-down current source 322 may generate a pull-down current IDN. Thelow voltage VL may have a lower voltage level than the high voltage VH.The pull-down current source 322 may be implemented by at least oneN-channel MOS transistor configured to a bias voltage or a currentcontrol signal. The capacitor 323 may be coupled to the output node ONat one end and may be coupled to the node, from which the low voltage VLis provided, at the other node. The voltage level of the output node ONand the delay control voltage VC may change depending on an amount ofcharge that is charged into the capacitor 323.

The first switch 324 may receive the up signal UP. The first switch 324may couple the pull-up current source 321 to the output node ON based onthe up signal UP. When the first switch 324 is turned on according tothe up signal UP, the pull-up current IUP may be provided to the outputnode ON and the capacitor 323 may be charged. Therefore, the voltagelevel of the output node ON and the delay control voltage VC may rise.The second switch 325 may receive the down signal DN. The second switch325 may couple the pull-down current source 322 to the output node ONbased on the down signal DN. When the second switch 325 is turned onaccording to the down signal DN, the pull-down current IDN may flow fromthe output node ON to the node, from which the low voltage VL isprovided, and the capacitor 323 may be discharged. Therefore, thevoltage level of the output node ON and the delay control voltage VC maylower.

There may be delay mismatch in the second phase detector 222 due tolocal process variation between the first set of plural drivers 311 andthe second set of plural drivers 312. Therefore, there may occur anerror between a time, at which the up signal UP is enabled according toa rising edge of the first internal clock signal ICLKD, and a time, atwhich the down signal DN is enabled according to a rising edge of thesecond feedback clock signal FBCLK2. Further, since the pull-up currentsource 321 is configured by a P-channel MOS transistor and the pull-downcurrent source 322 is configured by an N-channel MOS transistor in thecharge pump 223, there may occur an error in sizes between the pull-upcurrent IUP and the pull-down current IDN in spite of size adjustment ofthe transistors when designed. Therefore, there should occur a phaseerror between the first internal clock signal ICLKD and the secondfeedback clock signal FBCLK2 even when the second delay locked loop 220illustrated in FIG. 2 completes a delay-locking operation. The phaseerror may be represented by a following equation.Δt2=Δt _(MIS) +t _(RESET)*(1−IUP/IDN)

In the above equation, “Δt2” may represent the phase error between thefirst internal clock signal ICLKD and the second feedback clock signalFBCLK2 when the second delay locked loop 220 is locked, “Δt_(MIS)” mayrepresent the delay mismatch by the second phase detector 222 and“t_(RESET) ^(”) may represent the predetermined time when the up signalUP and the down signal DN are reset. In general, in order to improve“Δt2”, the amount of the pull-up current IUP and the pull-down currentIDN which are provided for the charge pump 223 to generate the delaycontrol voltage VC may be adjusted. However, it may be difficult toimplement high resolution by the scheme of adjusting the current amountof the charge pump 223 and the mismatch may occur again between theadjusted pull-up current IUP and pull-down current IDN. Therefore, itmay be difficult to fundamentally resolve the phase error between thefirst internal clock signal ICLKD and the second feedback clock signalFBCLK2.

FIG. 4 is a diagram illustrating a configuration of an analog delaylocked loop 400 in accordance with an embodiment. The analog delaylocked loop 400 may be applied as the second delay locked loop 122illustrated in FIG. 1 . The analog delay locked loop 400 may replace thesecond delay locked loop 220 illustrated in FIG. 2. The analog delaylocked loop 400 may include a delay line 410, a calibration circuit 420,a phase detector 430 and a charge pump 440. The delay line 410 receivesthe reference clock signal REFCLK and the delay control voltage VC. Whenthe analog delay locked loop 400 replaces the second delay locked loop220 illustrated in FIG. 2 , the reference clock signal REFCLK maycorrespond to the delay locked clock signal CLKDLL. The delay line 410may delay the reference clock signal REFCLK based on the delay controlvoltage VC to generate the plurality of delayed clock signals. The delayline 410 may output one among the plurality of delayed clock signals asthe internal reference clock signal and may output another one among theplurality of delayed clock signals as the feedback clock signal FBCLK.The delay line 410 may generate four among the plurality of delayedclock signals, as the first internal clock signal ICLKD, the secondinternal clock signal QCLKD, the third internal clock signal IBCLKD andthe fourth internal clock signal QBCLKD. The delay line 410 may providethe first internal clock signal ICLKD as the internal reference clocksignal. The delay line 410 may include a plurality of delay cells DC1 toDC9 respectively configured to output the plurality of delayed clocksignals. The configurations of the delay line 410 may be the same as theconfigurations of the second delay line 221 and thus redundantdescription about the same elements will be omitted.

The calibration circuit 420 may receive the first internal clock signalICLKD and the feedback clock signal FBCLK. The calibration circuit 420may generate a delayed reference clock signal REFD from the referenceclock signal based on the phases of the first internal clock signalICLKD and the feedback clock signal FBCLK. The calibration circuit 420may generate a delayed feedback clock signal FEBD from the feedbackclock signal FBCLK. The calibration circuit 420 may change the delayamount of the first internal clock signal ICLKD and the delay amount ofthe feedback clock signal FBCLK according to relative phases of thefirst internal clock signal ICLKD and the feedback clock signal FBCLK.The calibration circuit 420 may delay, for a longer time, a clock signalhaving a lagging phase to the other clock signal between the firstinternal clock signal ICLKD and the feedback clock signal FBCLK. Forexample, when the first internal clock signal ICLKD has a leading phaseto the feedback clock signal FBCLK, the calibration circuit 420 maydelay the first internal clock signal ICLKD for a first time to generatethe delayed reference clock signal REFD and may delay the feedback clocksignal FBCLK for a second time to generate the delayed feedback clocksignal FEBD. The second time may be longer than the first time. Forexample, when the first internal clock signal ICLKD has a lagging phaseto the feedback clock signal FBCLK, the calibration circuit 420 maydelay the first internal clock signal ICLKD for the second time togenerate the delayed reference clock signal REFD and may delay thefeedback clock signal FBCLK for the first time to generate the delayedfeedback clock signal FEBD.

The phase detector 430 may receive the delayed reference clock signalREFD and the delayed feedback clock signal FEBD. The phase detector 430may detect the phases of the delayed reference clock signal REFD and thedelayed feedback clock signal FEBD to generate a phase detection signalPD. The phase detection signal PD may include the up signal UP and thedown signal DN. The charge pump 440 may generate the delay controlvoltage VC based on the phase detection signal PD. The phase detector430 and the charge pump 440 may have the same configurations and mayperform the same operations as the second phase detector 222 and thecharge pump 223 illustrated in FIGS. 2 and 3 . Redundant descriptionabout the same configurations will be omitted.

The calibration circuit 420 may include a timing skew detector 421, acalibration signal generator 422 and a delay adjuster 423. The timingskew detector 421 may detect phase difference between the first internalclock signal ICLKD and the feedback clock signal FBCLK. The timing skewdetector 421 may detect the phase difference between the first internalclock signal ICLKD and the feedback clock signal FBCLK to generate afirst phase adjustment signal FEBINC and a second phase adjustmentsignal REFINC. The timing skew detector 421 may detect the phasedifference between the first internal clock signal ICLKD and thefeedback clock signal FBCLK to generate a first skew detection signaland a second skew detection signal. The timing skew detector 421 maygenerate the first phase adjustment signal FEBINC and the second phaseadjustment signal REFINC according to whether the logic levels of thefirst skew detection signal and the second skew detection signal staykept for an time corresponding to at least double of a unit cycle. Thetime corresponding to at least double of the unit cycle may be a loopbandwidth of the calibration circuit 420 and may represent a period whenthe calibration circuit 420 is updated. The loop bandwidth of thecalibration circuit 420 may be smaller than a loop bandwidth of theanalog delay locked loop 400. The period when the calibration circuit420 is updated may be greater than a period when the analog delay lockedloop 400 is updated. In an embodiment, the loop bandwidth of thecalibration circuit 420 may be set as three times of the unit cycle orgreater. The unit cycle may be determined on the basis of the pluralityof delayed clock signals generated from the delay line 410. The unitcycle will be described later.

The calibration signal generator 422 may receive the first phaseadjustment signal FEBINC and the second phase adjustment signal REFINCto generate a calibration signal CAL<1:2N>. The calibration signalCAL<1:2N> may be a digital code signal having a plurality of bits. Thecalibration signal generator 422 may change a value of a part of thecalibration signal CAL<1:2N> based on the first phase adjustment signalFEBINC. The calibration signal generator 422 may change a value of aremaining part of the calibration signal CAL<1:2N> based on the secondphase adjustment signal REFINC. For example, the calibration signalCAL<1:2N> may have 2N number of bits. Here, N is an integer equal to orgreater than 2. The calibration signal generator 422 may change a valueof first to N^(th) bits CAL<1:N> of the calibration signal CAL<1:2N>based on the first phase adjustment signal FEBINC. The calibrationsignal generator 422 may change a value of (N+1)^(th) to 2N^(th) bitsCAL<N+1:2N> of the calibration signal CAL<1:2N> based on the secondphase adjustment signal REFINC. The calibration signal generator 422 mayinclude configurations such as a decoding circuit, a shift registercircuit and so forth such that the calibration signal generator 422decodes the first phase adjustment signal FEBINC and the second phaseadjustment signal REFINC and changes a value of the first to 2N^(th)bits CAL<1:2N> of the calibration signal CAL<1:2N> according to theresult of the decoding.

The delay adjuster 423 may receive the calibration signal CAL<1:2N>. Thedelay adjuster 423 may delay the first internal clock signal ICLKD basedon a part of the calibration signal CAL<1:2N> to generate the delayedreference clock signal REFD. The delay adjuster 423 may delay thefeedback clock signal FBCLK based on a remaining part of the calibrationsignal CAL<1:2N> to generate the delayed feedback clock signal FEBD. Thedelay adjuster 423 may delay the first internal clock signal ICLKD by apredetermined amount based on the first to N^(th) bits CAL<1:N> of thecalibration signal CAL<1:2N> to generate the delayed reference clocksignal REFD. The delay adjuster 423 may delay the feedback clock signalFBCLK by a predetermined amount based on the (N+1)^(th) to 2N^(th) bitsCAL<N+1:2N> of the calibration signal CAL<1:2N> to generate the delayedfeedback clock signal FEBD.

FIG. 5 is a diagram illustrating a configuration of timing skew detector421 illustrated in FIG. 4 . Referring to FIG. 5 , the timing skewdetector 421 may include a skew detector 510, a filter 520 and a phaseadjustment signal generator 530. The skew detector 510 may detect thephases of the first internal clock signal ICLKD and the feedback clocksignal FBCLK to generate a first skew detection signal SKW1 and a secondskew detection signal SKW2. The first skew detection signal SKW1 mayinclude information on whether the first internal clock signal ICLKD hasa leading phase or a lagging phase to the feedback clock signal FBCLK.The second skew detection signal SKW2 may include information on whetherthe feedback clock signal FBCLK has a leading phase or a lagging phaseto the first internal clock signal ICLKD.

The filter 520 may receive the first skew detection signal SKW1 and thesecond skew detection signal SKW2. The filter 520 may generate a firstphase information signal SLOW and a second phase information signal FASTbased on the first skew detection signal SKW1 and the second skewdetection signal SKW2. The first phase information signal SLOW may beenabled when the feedback clock signal FBCLK has a lagging phase to thefirst internal clock signal ICLKD. The second phase information signalFAST may be enabled with the feedback clock signal FBCLK has a leadingphase to the first internal clock signal ICLKD. The filter 520 maydefine the loop bandwidth of the calibration circuit 420 based on oneamong the plurality of delayed clock signals. The filter 520 maygenerate the first phase information signal SLOW and the second phaseinformation signal FAST based on whether the logic levels of the firstskew detection signal SKW1 and the second skew detection signal SKW2stay kept at the same logic level, for a time corresponding to the loopbandwidth.

The phase adjustment signal generator 530 may receive the first phaseinformation signal SLOW and the second phase information signal FAST.The phase adjustment signal generator 530 may generate the first phaseadjustment signal FEBINC based on the first phase information signalSLOW. The phase adjustment signal generator 530 may generate the secondphase adjustment signal REFINC based on the second phase informationsignal FAST.

The skew detector 510 may include a first flip-flop 511 and a secondflip-flop 512. Each of the first flip-flop 511 and the second flip-flop512 may be a D flip-flop. The first flip-flop 511 may receive the firstinternal clock signal ICLKD at its input node D, may receive thefeedback clock signal FBCLK at its clock node and may output the firstskew detection signal SKW1 at its output node Q. The second flip-flop512 may receive the feedback clock signal FBCLK at its input node D, mayreceive the first internal clock signal ICLKD at its clock node and mayoutput the second skew detection signal SKW2 at its output node Q. Inorder to reduce a malfunction that can occur due to variation of setuptimes and hold times of the first flip-flop 511 and the second flip-flop512, the skew detector 510 may detect a skew between phases of the firstinternal clock signal ICLKD and the feedback clock signal FBCLK in adual mode.

The filter 520 may include a first flip-flop 521, a second flip-flop522, a third flip-flop 523, a fourth flop-flop 524, a first gatingcircuit 525 and a second gating circuit 526. Each of the first to fourthflip-flops 521, 522, 523 and 524 may be a D flip-flop. The firstflip-flop 521 may receive the first skew detection signal SKW1 at itsinput node D, may receive a first clock signal EVCLK at its clock nodeand may output a first even signal EV1 at its output node Q. The secondflip-flop 522 may receive the second skew detection signal SKW2 at itsinput node D, may receive the first clock signal EVCLK at its clock nodeand may output a second even signal EV2 at its output node Q. The thirdflip-flop 523 may receive the first skew detection signal SKW1 at itsinput node D, may receive a second clock signal ODCLK at its clock nodeand may output a first odd signal OD1 at its output node Q. The secondclock signal ODCLK may have a lagging phase to the first clock signalEVCLK. The fourth flop-flop 524 may receive the second skew detectionsignal SKW2 at its input node D, may receive the second clock signalODCLK at its clock node and may output a second odd signal OD2 at itsoutput node Q.

The first gating circuit 525 may receive the first even signal EV1, thefirst odd signal OD1, the second even signal EV2 and the second oddsignal OD2. The first gating circuit 525 may perform an AND operation onthe received signals to generate the first phase information signalSLOW. The first gating circuit 525 may include an AND gate. The firstgating circuit 525 may receive the first even signal EV1, the first oddsignal OD1, an inverted signal of the second even signal EV2 and aninverted signal of the second odd signal OD2 to generate the first phaseinformation signal SLOW. The second gating circuit 526 may receive thefirst even signal EV1, the first odd signal OD1, the second even signalEV2 and the second odd signal OD2. The second gating circuit 526 mayperform an AND operation on the received signal to generate the secondphase information signal FAST. The second gating circuit 526 may includean AND gate. The second gating circuit 526 may receive an invertedsignal of the first even signal EV1, an inverted signal of the first oddsignal OD1, the second even signal EV2 and the second odd signal OD2 togenerate the second phase information signal FAST. In order to reducethe loop bandwidth of the calibration circuit 420 and increase theupdate period of the calibration circuit 420, the filter 520 may furtherinclude an additional flip-flop. The additional flip-flop may receive aclock signal having a lagging phase to the second clock signal ODCLK.The gating circuits may be modified to further receive a signal outputfrom the additional flip-flop.

The first gating circuit 525 may output, when the first even signal EV1and the first odd signal OD1 are of a logic high level and the secondeven signal EV2 and the second odd signal OD2 are of a logic low level,the first phase information signal SLOW of a logic high level. Thesecond gating circuit 526 may output, when the first even signal EV1 andthe first odd signal OD1 are of a logic low level and the second evensignal EV2 and the second odd signal OD2 are of a logic high level, thesecond phase information signal FAST of a logic high level. The firsteven signal EV1 and the second even signal EV2 may be generated insynchronization with the first clock signal EVCLK. The first odd signalOD1 and the second odd signal OD2 may be generated in synchronizationwith the second clock signal ODCLK. Therefore, the filter 520 may enablethe first phase information signal SLOW and the second phase informationsignal FAST to a logic high level only when the logic levels of thefirst skew detection signal SKW1 and the second skew detection signalSKW2 are kept at the logic high level until transitions of the firstclock signal EVCLK and the second clock signal ODCLK are generated. Ingeneral, a delay locked loop may cause a bang-bang jitter and thus anincorrect calibration operation may be performed in a case of generatingphase information signal directly from the first skew detection signalSKW1 and the second skew detection signal SKW2. In accordance with anembodiment, a value of a calibration signal may change according to aphase information signal only when the logic levels of the first skewdetection signal SKW1 and the second skew detection signal SKW2 are keptat a same logic level for a predetermined time. Therefore, a precisecalibration operation may be performed.

The phase adjustment signal generator 530 may include a first gatingcircuit 531, a second gating circuit 532 and a third gating circuit 533.The first gating circuit 531 may receive the first phase informationsignal SLOW and the second phase information signal FAST to generate acalibration enable signal CALON. The first gating circuit 531 mayperform an OR operation on the first phase information signal SLOW andthe second phase information signal FAST to generate the calibrationenable signal CALON. The first gating circuit 531 may include an ORgate. The first gating circuit 531 may enable, when at least one betweenthe first phase information signal SLOW and the second phase informationsignal FAST is enabled to a logic high level, the calibration enablesignal CALON to a logic high level. The second gating circuit 532 mayreceive the first phase information signal SLOW, the calibration enablesignal CALON and a third clock signal ODCLKB. The third clock signalODCLKB may have a lagging phase to the second clock signal ODCLK. Thesecond gating circuit 532 may perform an AND operation on the firstphase information signal SLOW, the calibration enable signal CALON andthe third clock signal ODCLKB to generate the first phase adjustmentsignal FEBINC. The second gating circuit 532 may include an AND gate.The second gating circuit 532 may enable the first phase adjustmentsignal FEBINC to a logic high level when both of the first phaseinformation signal SLOW and the calibration enable signal CALON are of alogic high level while the third clock signal ODCLKB is of a logic highlevel. The third gating circuit 533 may receive the second phaseinformation signal FAST, the calibration enable signal CALON and thethird clock signal ODCLKB. The third gating circuit 533 may perform anAND operation on the second phase information signal FAST, thecalibration enable signal CALON and the third clock signal ODCLKB togenerate the second phase adjustment signal REFINC. The third gatingcircuit 533 may include an AND gate. The third gating circuit 533 mayenable the second phase adjustment signal REFINC to a logic high levelwhen both of the second phase information signal FAST and thecalibration enable signal CALON are of a logic high level while thethird clock signal ODCLKB is of a logic high level.

The timing skew detector 421 may further include a control clockgenerator 540. The control clock generator 540 may receive one among theplurality of delayed clock signals generated from the voltage-controlleddelay line 410 illustrated in FIG. 4 . For example, the control clockgenerator 540 may receive the delayed clock signal CLK4 output from thefourth delay cell DC4 of the voltage-controlled delay line 410. Thecontrol clock generator 540 may generate the first clock signal EVCLK,the second clock signal ODCLK and the third clock signal ODCLKB from thedelayed clock signal CLK4. The control clock generator 540 may include afirst divider 541, a first inverter 542, a second divider 543, a thirddivider 544 and a second inverter 545. The first divider 541 may dividethe delayed clock signal CLK4. The first inverter 542 may invert theoutput of the first divider 541. The second divider 543 may divide theoutput of the first inverter 542 to generate the first clock signalEVCLK. The third divider 544 may divide the output of the first divider541 to generate the second clock signal ODCLK. The second inverter 545may invert the second clock signal ODCLK to generate the third clocksignal ODCLKB.

FIG. 6 is a diagram illustrating a configuration of the delay adjuster423 illustrated in FIG. 4 . Referring to FIG. 6 , the delay adjuster 423may include a first variable delayer 610 and a second variable delayer620. The first variable delayer 610 may receive the first internal clocksignal ICLKD and the first to N^(th) bits CAL<1:N> of the calibrationsignal CAL<1:2N> to generate the delayed reference clock signal REFD. Adelay amount of the first variable delayer 610 may be set on the basisof the first to N^(th) bits CAL<1:N> of the calibration signalCAL<1:2N>. The first variable delayer 610 may delay the first internalclock signal ICLKD by the set delay time to generate the delayedreference clock signal REFD. The second variable delayer 620 may receivethe feedback clock signal FBCLK and the (N+1)^(th) to 2N^(th) bitsCAL<N+1:2N> of the calibration signal CAL<1:2N> to generate the delayedfeedback clock signal FEBD. A delay amount of the second variabledelayer 620 may be set on the basis of the (N+1)^(th) to 2N^(th) bitsCAL<N+1:2N> of the calibration signal CAL<1:2N>. The second variabledelayer 620 may delay the feedback clock signal FBCLK by the set delaytime to generate the delayed feedback clock signal FEBD.

FIG. 7 is a timing diagram illustrating operations of the calibrationcircuit 420 and the analog delay locked loop 400 in accordance with anembodiment. Hereinafter, described with reference to FIGS. 3 to 6 willbe the operations of the calibration circuit 420 and the analog delaylocked loop 400. In S1, the skew detector 510 of the timing skewdetector 421 may detect the phases of the first internal clock signalICLKD and the feedback clock signal FBCLK to generate the first skewdetection signal SKW1 and the second skew detection signal SKW2. Asillustrated in FIG. 7 , when the first internal clock signal ICLKD has alagging phase to the feedback clock signal FBCLK due to the phase error“Δt2” caused by the phase detector 430 and the charge pump 440, the skewdetector 510 may generate the first skew detection signal SKW1 having alogic low level and the second skew detection signal SKW2 having a logichigh level. The calibration signal CAL<1:2N> may keep a default valuebefore update. The delay adjuster 423 may delay the first internal clocksignal ICLKD and the feedback clock signal FBCLK by the same time togenerate the delayed reference clock signal REFD and the delayedfeedback clock signal FEBD. The phase detector 430 may enable the downsignal DN when the delayed feedback clock signal FEBD transitions from alogic low level to a logic high level. The phase detector 430 may enablethe up signal UP when the first internal clock signal ICLKD transitionsfrom a logic low level to a logic high level. The up signal UP and thedown signal DN may stay enabled until reset. A pulse width of the downsignal DN may be wider than a pulse width of the up signal UP. In anideal case, the charge pump 440 should generate the delay controlvoltage VC having a lower level based on the up signal UP and the downsignal DN. However, when the pull-up current IUP is greater than thepull-down current IDN due to the mismatch between the pull-up currentIUP and the pull-down current IDN of the charge pump 440, there mayoccur a malfunction that the voltage level of the delay control voltageVC cannot lower and stays to a previous voltage level. Therefore, it isimpossible, only by the phase detector 430 and the charge pump 440, tomatch the phases of the first internal clock signal ICLKD and thefeedback clock signal FBCLK. When the logic levels of the first skewdetection signal SKW1 and the second skew detection signal SKW2 are keptat a same logic level for a predetermined time, the filter 520 of thecalibration circuit 420 may keep the first phase information signal SLOWdisabled and may enable the second phase information signal FAST to alogic high level.

In S2, the phase adjustment signal generator 530 may enable the secondphase adjustment signal REFINC according to the second phase informationsignal FAST. The calibration signal generator 422 may increase the valueof the (N+1)^(th) to 2N^(th) bits CAL<N+1:2N> of the calibration signalCAL<1:2N>. The delay adjuster 423 may delay the feedback clock signalFBCLK by a relatively longer time to generate the delayed feedback clocksignal FEBD. The delay adjuster 423 may delay the first internal clocksignal ICLKD by a relatively shorter time to generate the delayedreference clock signal REFD. Therefore, the phase difference between thedelayed reference clock signal REFD and the delayed feedback clocksignal FEBD may become greater than the phase difference between thefirst internal clock signal ICLKD and the feedback clock signal FBCLK.The delayed reference clock signal REFD may be further delayed than thedelayed feedback clock signal FEBD by a calibrated phase “Δt3”, which isset by a calibration operation. The phase detector 430 may enable thedown signal DN when the delayed feedback clock signal FEBD transitionsfrom a logic low level to a logic high level. The phase detector 430 mayenable the up signal UP when the delayed reference clock signal REFDtransitions from a logic low level to a logic high level. The up signalUP and the down signal DN may stay enabled until reset. The up signal UPmay have the same pulse width as the up signal UP generated in S1. Thedown signal DN may have a greater pulse width than the down signal DNgenerated in S1. The charge pump 440 may pull-down the delay controlvoltage VC for a longer time according to the down signal DN. Therefore,the voltage level of the delay control voltage VC may lower even whenthe pull-up current IUP is greater than the pull-down current IDN.

In S3, when the voltage level of the delay control voltage VC lowers,the phased of the first internal clock signal ICLKD and the feedbackclock signal FBCLK, which are generated from the delay line 410, may bematched. The delayed reference clock signal REFD and the delayedfeedback clock signal FEBD may have lagging phases to the delayedreference clock signal REFD and the delayed feedback clock signal FEBDillustrated in S2. Therefore, the voltage level of the delay controlvoltage VC may become lower than the voltage level of the delay controlvoltage VC illustrated in S2. Since the phases of the first internalclock signal ICLKD and the feedback clock signal FBCLK are matched, thecalibration circuit 420 may terminate the calibration operation and maykeep the value of the calibration signal CAL<1:2N>. The delay adjuster423 may further delay the first internal clock signal ICLKD with respectto the feedback clock signal FBCLK by the delay time, which is set bythe calibration operation, to generate the delayed reference clocksignal REFD. Therefore, the delayed reference clock signal REFD may havea lagging phase, by an amount of the calibrated phase “Δt3” that is setby the calibration operation, to the delayed feedback clock signal FEBD.The phase difference between the delayed reference clock signal REFD andthe delayed feedback clock signal FEBD may compensate for the phaseerror “Δt2” caused by the local process variation of the phase detector430 and the mismatch between pull-up current IUP and the pull-downcurrent IDN of the charge pump 440. The delay control voltage VCgenerated from the charge pump 440 may keep having a specific level.Therefore, the analog delay locked loop 400 may generate the firstinternal clock signal ICLKD and the feedback clock signal FBCLK, ofwhich the phases are matched by the calibration circuit 420.

FIG. 8A is a diagram illustrating a configuration of a delay line 800 inaccordance with an embodiment. FIG. 8B is a timing diagram illustratingan operation of the delay line 800 illustrated in FIG. 8A. The delayline 800 may be applied as a part of each of the second delay line 221and the delay line 410 respectively illustrated in FIGS. 2 and 4 .Referring to FIG. 8A, the delay line 800 may include a first delay cell810 and a second delay cell 820. The first delay cell 810 may invert aninput signal IN to generate a first output signal OUT1. The first delaycell 810 may inversion-drive the first output signal OUT1 to output afirst delayed clock signal DCLK1. The second delay cell 820 may invertthe first output signal OUT1 to generate a second output signal OUT2.The second delay cell 820 may inversion-drive the second output signalOUT2 to output a second delayed clock signal DCLK2. Pull-down drivingforce, with which the first delay cell 810 pulls down the first outputsignal OUT1 according to the input signal IN, may change based on thedelay control voltage VC. When the pull-down driving force of the firstdelay cell 810 changes, a delay amount of the first delay cell 810 maychange. Pull-down driving force, with which the second delay cell 820pulls down the second output signal OUT2 according to the first outputsignal OUT1, may change based on the delay control voltage VC. When thepull-down driving force of the second delay cell 820 changes, a delayamount of the second delay cell 820 may change. In an embodiments, avoltage level outputted from the delay cell may be quickly changed andthe delay amount of the delay cell may be decreased as the pull-downdriving force of the delay cell is increased. The voltage leveloutputted from the delay cell may be slowly changed and the delay amountof the delay cell may be increased as the pull-down driving force of thedelay cell is decreased.

The first delay cell 810 may include a first inverter 811 and a firstcurrent source 812. The first inverter 811 may receive the input signalIN and may invert the input signal IN to generate the first outputsignal OUT1. The first inverter 811 may be coupled between a node, fromwhich the high voltage VH is provided, and a node, from which the lowvoltage VL is provided. The first inverter 811 may invert the inputsignal IN. The high voltage VH may have a higher voltage level than thelow voltage VL. The first current source 812 may be coupled between thefirst inverter 811 and the node, from which the low voltage VL isprovided. The first current source 812 may receive the delay controlvoltage VC. The first current source 812 may change the pull-downdriving force of the first inverter 811 based on the delay controlvoltage VC to change the delay amount of the first delay cell 810. Thefirst delay cell 810 may further include a second inverter 813. Thesecond inverter 813 may inversion-drive the first output signal OUT1 tooutput the first delayed clock signal DCLK1.

The second delay cell 820 may include a third inverter 821 and a secondcurrent source 822. The third inverter 821 may receive the first outputsignal OUT1 and may invert the first output signal OUT1 to generate thesecond output signal OUT2. The third inverter 821 may be coupled betweenthe node, from which the high voltage VH is provided, and the node, fromwhich the low voltage VL provided. The third inverter 821 may invert thefirst output signal OUT1. The second current source 822 may be coupledbetween the third inverter 821 and the node, from which the low voltageVL is provided. The second current source 822 may receive the delaycontrol voltage VC. The second current source 822 may change thepull-down driving force of the third inverter 821 based on the delaycontrol voltage VC to change the delay amount of the second delay cell820. The second delay cell 820 may further include a fourth inverter823. The fourth inverter 823 may inversion-drive the second outputsignal OUT2 to output the second delayed clock signal DCLK2.

The first inverter 811 may include a first transistor M1 and a secondtransistor M2. The first transistor M1 may be a P-channel MOStransistor. The second transistor M2 may be a N-channel MOS transistor.The first current source 812 may include a third transistor M3. Thethird transistor M3 may be a N-channel MOS transistor. The firsttransistor M1 may receive the input signal IN at its gate, may becoupled to the node, from which the high voltage VH is provided, at itssource and may be coupled to a first output node ON1 at its drain. Thefirst output signal OUT1 may be output through the first output nodeON1. The second transistor M2 may receive the input signal IN at itsgate and may be coupled to the first output node ON1 at its drain. Thethird transistor M3 may receive the delay control voltage VC at itsgate, may be coupled at its drain to the source of the second transistorM2 and may be coupled to the node, from which the low voltage VL isprovided, at its source. The third transistor M3 may change an amount ofcurrent flowing from the source of the second transistor M2 to the node,from which the low voltage VL is provided, based on the delay controlvoltage VC.

The third inverter 821 may include a fourth transistor M4 and a fifthtransistor M5. The fourth transistor M4 may be a P-channel MOStransistor. The fifth transistor M5 may be a N-channel MOS transistor.The second current source 822 may include a sixth transistor M6. Thesixth transistor M6 may be a N-channel MOS transistor. The fourthtransistor M4 may receive the first output signal OUT1 at its gate, maybe coupled to the node, from which the high voltage VH is provided, atits source and may be coupled to a second output node ON2 at its drain.The second output signal OUT2 may be output through the second outputnode ON2. The fifth transistor M5 may receive the first output signalOUT1 at its gate and may be coupled to the second output node ON2 at itsdrain. The sixth transistor M6 may receive the delay control voltage VCat its gate, may be coupled at its drain to the source of the fifthtransistor M5 and may be coupled to the node, from which the low voltageVL is provided, at its source. The sixth transistor M6 may change anamount of current flowing from the source of the fifth transistor M5 tothe node, from which the low voltage VL is provided, based on the delaycontrol voltage VC.

The delay line 800 has an advantage that the delay amounts of the firstdelay cell 810 and the second delay cell 820 can change based on thedelay control voltage VC, which is an analog signal, and thus the delayvariation is reduced and the phase skew is reduced in spite of a highfrequency of the input signal IN input to the delay line 800. However,due to the characteristic of the N-channel MOS transistor that lossoccurs in a threshold voltage and the voltage level variation that highboundary of the voltage level is increased, there is a problem that thefirst output signal OUT1 and the second output signal OUT2 cannot fullyswing to the voltage level of the low voltage VL, as illustrated in FIG.8B. When the first output signal OUT1 and the second output signal OUT2cannot fully swing, a waveform of a final output signal becomes moredistorted as a number of delay cells becomes greater and a preciseoutput signal cannot be generated at a high-speed operation.

FIG. 9A is a diagram illustrating a configuration of a delay line 900 inaccordance with an embodiment. FIG. 9B is a timing diagram illustratingan operation of the delay line 900 illustrated in FIG. 9A. The delayline 900 may be applied as a part of each of the second delay line 221and the delay line 410 respectively illustrated in FIGS. 2 and 4 .Referring to FIG. 9A, the delay line 900 may include a first delay cell910 and a second delay cell 920. The first delay cell 910 may invert aninput signal IN to generate a first output signal OUT1. The first delaycell 910 may inversion-drive the first output signal OUT1 to output afirst delayed clock signal DCLK1. The second delay cell 920 may invertthe first output signal OUT1 to generate a second output signal OUT2.The second delay cell 920 may inversion-drive the second output signalOUT2 to output a second delayed clock signal DCLK2. Pull-down drivingforce, with which the first delay cell 910 pulls down the first outputsignal OUT1 according to the input signal IN, may change based on thedelay control voltage VC and the second output signal OUT2. When thepull-down driving force of the first delay cell 910 changes, a delayamount of the first delay cell 910 may change. Pull-down driving force,with which the second delay cell 920 pulls down the second output signalOUT2 according to the first output signal OUT1, may change based on thedelay control voltage VC. When the pull-down driving force of the seconddelay cell 920 changes, a delay amount of the second delay cell 920 maychange. In an embodiment, the second delay cell 920 may further receivean output signal OUT3 output from a subsequent delay cell, which isdisposed subsequently to the second delay cell 920 and configured toreceive the second output signal OUT2. The pull-down driving force andthe delay amount of the second delay cell 920 may change based on thedelay control voltage VC and the output signal OUT3 output from thesubsequent delay cell.

The first delay cell 910 may include a first inverter 911, a firstcurrent source 912 and a first feedback current source 913. The firstinverter 911 may receive the input signal IN and may invert the inputsignal IN to generate the first output signal OUT1. The first inverter911 may be coupled between a node, from which the high voltage VH isprovided, and a node, from which the low voltage VL is provided. Thefirst inverter 911 may invert the input signal IN. The first currentsource 912 may be coupled between the first inverter 911 and the node,from which the low voltage VL is provided. The first current source 912may receive the delay control voltage VC. The first current source 912may change the pull-down driving force of the first inverter 911 basedon the delay control voltage VC to change the delay amount of the firstdelay cell 910. The first feedback current source 913 may be coupledbetween the first inverter 911 and the node, from which the low voltageVL is provided. The first feedback current source 913 may receive thesecond output signal OUT2. The first feedback current source 913 mayfurther change the pull-down driving force of the first inverter 911based on the second output signal OUT2. The first delay cell 910 mayfurther include a second inverter 914. The second inverter 914 mayinversion-drive the first output signal OUT1 to output the first delayedclock signal DCLK1.

The second delay cell 920 may include a third inverter 921, a secondcurrent source 922 and a second feedback current source 923. The thirdinverter 921 may receive the first output signal OUT1 and may invert thefirst output signal OUT1 to generate the second output signal OUT2. Thethird inverter 921 may be coupled between the node, from which the highvoltage VH is provided, and the node, from which the low voltage VL isprovided. The third inverter 921 may invert the first output signalOUT1. The second current source 922 may be coupled between the thirdinverter 921 and the node, from which the low voltage VL is provided.The second current source 922 may receive the delay control voltage VC.The second current source 922 may change the pull-down driving force ofthe third inverter 921 based on the delay control voltage VC to changethe delay amount of the second delay cell 920. The second feedbackcurrent source 923 may be coupled between the third inverter 921 and thenode, from which the low voltage VL is provided. The second feedbackcurrent source 923 may receive the output signal OUT3 output from thesubsequent delay cell. The second feedback current source 923 mayfurther change the pull-down driving force of the third inverter 921based on the output signal OUT3 output from the subsequent delay cell.The second delay cell 920 may further include a fourth inverter 924. Thefourth inverter 924 may inversion-drive the second output signal OUT2 tooutput the second delayed clock signal DCLK2.

The first inverter 911 may include a first transistor T1 and a secondtransistor T2. The first transistor T1 may be a P-channel MOStransistor. The second transistor T2 may be a N-channel MOS transistor.The first current source 912 may include a third transistor T3. Thethird transistor T3 may be a N-channel MOS transistor. The firstfeedback current source 913 may include a fourth transistor T4. Thefourth transistor T4 may be a N-channel MOS transistor. The firsttransistor T1 may receive the input signal IN at its gate, may becoupled to the node, from which the high voltage VH is provided, at itssource and may be coupled to a first output node ON1 at its drain. Thefirst output signal OUT1 may be output through the first output nodeON1. The second transistor T2 may receive the input signal IN at itsgate and may be coupled to the first output node ON1 at its drain. Thethird transistor T3 may receive the delay control voltage VC at itsgate, may be coupled at its drain to the source of the second transistorT2 and may be coupled to the node, from which the low voltage VL isprovided, at its source. The third transistor T3 may change an amount ofcurrent flowing from the source of the second transistor T2 to the node,from which the low voltage VL is provided, based on the delay controlvoltage VC. The fourth transistor T4 may receive the second outputsignal OUT2 at its gate, may be coupled at its drain to the source ofthe second transistor T2 and may be coupled to the node, from which thelow voltage VL is provided, at its source. The fourth transistor T4 mayfurther change the amount of current flowing from the source of thesecond transistor T2 to the node, from which the low voltage VL isprovided, based on the second output signal OUT2.

The third inverter 921 may include a fifth transistor T5 and a sixthtransistor T6. The fifth transistor T5 may be a P-channel MOStransistor. The sixth transistor T6 may be a N-channel MOS transistor.The second current source 922 may include a seventh transistor T7. Theseventh transistor T7 may be a N-channel MOS transistor. The secondfeedback current source 923 may include an eighth transistor T8. Theeighth transistor T8 may be a N-channel MOS transistor. The fifthtransistor T5 may receive the first output signal OUT1 at its gate, maybe coupled to the node, from which the high voltage VH is provided, atits source and may be coupled to a second output node ON2 at its drain.The second output signal OUT2 may be output through the second outputnode ON2. The sixth transistor T6 may receive the first output signalOUT1 at its gate and may be coupled to the second output node ON2 at itsdrain. The seventh transistor T7 may receive the delay control voltageVC at its gate, may be coupled at its drain to the source of the sixthtransistor T6 and may be coupled to the node, from which the low voltageVL is provided, at its source. The seventh transistor T7 may change anamount of current flowing from the source of the sixth transistor T6 tothe node, from which the low voltage VL is provided, based on the delaycontrol voltage VC. The eighth transistor T8 may receive at its gate theoutput signal OUT3 output from the subsequent delay cell, may be coupledat its drain to the source of the sixth transistor T6 and may be coupledto the node, from which the low voltage VL is provided, at its source.The eighth transistor T8 may further change the amount of currentflowing from the source of the sixth transistor T6 to the node, fromwhich the low voltage VL is provided, based on the output signal OUT3output from the subsequent delay cell.

The delay line 900 may solve the problem, as illustrated in FIG. 8B,that the first output signal OUT1 and the second output signal OUT2cannot fully swing. The first feedback current source 913 and the secondfeedback current source 923 may further increase the amounts of currentrespectively flowing from the first inverter 911 and the third inverter921 to the node, from which the low voltage VL is provided, to furtherchange the pull-down driving force of the first delay cell 910 and thesecond delay cell 920. As illustrated in FIG. 9B, the first feedbackcurrent source 913 and the second feedback current source 923 mayrespectively receive the output signals fed-back from the delay cellsdisposed subsequently thereto and thus may further change the pull-downdriving force of the first delay cell 910 and the second delay cell 920.Therefore, the first feedback current source 913 and the second feedbackcurrent source 923 may allow the first output signal OUT1 and the secondoutput signal OUT2 to fully swing to the level of the low voltage VL.The first feedback current source 913 and the second feedback currentsource 923 may operate after the logic level of the fed-back outputsignal transitions. Therefore, the first feedback current source 913 andthe second feedback current source 923 may pull-down the first outputsignal OUT1 and the second output signal OUT2 to the level of the lowvoltage VL but the delay amounts of the delay cell 910 and the seconddelay cell 920 may not substantially change.

FIGS. 10A to 10C are diagrams illustrating configurations of delay lines1000A, 1000B and 1000C in accordance with an embodiment. Each of thedelay lines 1000A, 1000B and 1000C may be applied as a part of each ofthe second delay line 221 and the delay line 410 respectivelyillustrated in FIGS. 2 and 4 . Referring to FIG. 10A, the delay line1000A may include a first delay cell 10A and a second delay cell 20A.The first delay cell 10A may invert an input signal IN to generate afirst output signal OUT1. The first delay cell 10A may inversion-drivethe first output signal OUT1 to output a first delayed clock signalDCLK1. The second delay cell 20A may invert the first output signal OUT1to generate a second output signal OUT2. The second delay cell 20A mayinversion-drive the second output signal OUT2 to output a second delayedclock signal DCLK2. Pull-down driving force, with which the first delaycell 10A pulls down the first output signal OUT1 according to the inputsignal IN, may change based on the delay control voltage VC and thesecond output signal OUT2. Pull-down driving force, with which thesecond delay cell 20A pulls down the second output signal OUT2 accordingto the first output signal OUT1, may change based on the delay controlvoltage VC and an output signal OUT3 output from a subsequent delaycell, which is disposed subsequently to the second delay cell 20A andconfigured to receive the second output signal OUT2.

The first delay cell 10A may include a first inverter 11A, a firstcurrent source 12A and a first feedback current source 13A. The firstinverter 11A may receive the input signal IN and may invert the inputsignal IN to generate the first output signal OUT1. The first inverter11A may be coupled between a node, from which the high voltage VH isprovided, and a node, from which the low voltage VL is provided. Thefirst inverter 11A may invert the input signal IN. The first currentsource 12A may be coupled between the first inverter 11A and the node,from which the low voltage VL is provided. The first current source 12Amay receive the delay control voltage VC. The first current source 12Amay change the pull-down driving force of the first inverter 11A basedon the delay control voltage VC to change the delay amount of the firstdelay cell 10A. The first feedback current source 13A may be coupledbetween the first inverter 11A and the node, from which the low voltageVL is provided. The first feedback current source 13A may receive thesecond output signal OUT2. The first feedback current source 13A mayfurther change the pull-down driving force of the first inverter 11Abased on the second output signal OUT2. In an embodiment, the firstfeedback current source 13A may further receive a first switching signalSW1. The first feedback current source 13A may be selectively coupled tothe first inverter 11A according to the first switching signal SW1. Thefirst delay cell 10A may further include a second inverter 14A. Thesecond inverter 14A may inversion-drive the first output signal OUT1 tooutput the first delayed clock signal DCLK1.

In an embodiment, the first delay cell 10A may further include a firstauxiliary current source 15A. The first auxiliary current source 15A maybe coupled between the first inverter 11A and the node, from which thelow voltage VL is provided. The first auxiliary current source 15A mayreceive the delay control voltage VC. The first auxiliary current source15A may further change the pull-down driving force of the first inverter11A based on the delay control voltage VC. In an embodiment, the firstauxiliary current source 15A may further receive a second switchingsignal SW2. The first auxiliary current source 15A may be selectivelycoupled to the first inverter 11A according to the second switchingsignal SW2.

The second delay cell 20A may include a third inverter 21A, a secondcurrent source 22A and a second feedback current source 23A. The thirdinverter 21A may receive the first output signal OUT1 and may invert thefirst output signal OUT1 to generate the second output signal OUT2. Thethird inverter 21A may be coupled between the node, from which the highvoltage VH is provided, and the node, from which the low voltage VL isprovided. The third inverter 21A may invert the first output signalOUT1. The second current source 22A may be coupled between the thirdinverter 21A and the node, from which the low voltage VL is provided.The second current source 22A may receive the delay control voltage VC.The second current source 22A may change the pull-down driving force ofthe third inverter 21A based on the delay control voltage VC to changethe delay amount of the second delay cell 20A. The second feedbackcurrent source 23A may be coupled between the third inverter 21A and thenode, from which the low voltage VL is provided. The second feedbackcurrent source 23A may receive the output signal OUT3 output from thesubsequent delay cell. The second feedback current source 23A mayfurther change the pull-down driving force of the third inverter 21Abased on the output signal OUT3 output from the subsequent delay cell.In an embodiment, the second feedback current source 23A may furtherreceive the first switching signal SW1. The second feedback currentsource 23A may be selectively coupled to the third inverter 21Aaccording to the first switching signal SW1. The second delay cell 20Amay further include a fourth inverter 24A. The fourth inverter 24A mayinversion-drive the second output signal OUT2 to output the seconddelayed clock signal DCLK2.

In an embodiment, the second delay cell 20A may further include a secondauxiliary current source 25A. The second auxiliary current source 25Amay be coupled between the third inverter 21A and the node, from whichthe low voltage VL is provided. The second auxiliary current source 25Amay receive the delay control voltage VC. The second auxiliary currentsource 25A may further change the pull-down driving force of the thirdinverter 21A based on the delay control voltage VC. In an embodiment,the second auxiliary current source 25A may further receive the secondswitching signal SW2. The second auxiliary current source 25A may beselectively coupled to the third inverter 21A according to the secondswitching signal SW2.

The first inverter 11A may include a first transistor T11 and a secondtransistor T12. The first transistor T11 may be a P-channel MOStransistor. The second transistor T12 may be a N-channel MOS transistor.The first current source 12A may include a third transistor T13. Thethird transistor T13 may be a N-channel MOS transistor. The firstfeedback current source 13A may include a fourth transistor T14 and afifth transistor T15. Each of the fourth transistor T14 and the fifthtransistor T15 may be a N-channel MOS transistor. The first auxiliarycurrent source 15A may include a sixth transistor T16 and a seventhtransistor T17. Each of the sixth transistor T16 and the seventhtransistor T17 may be a N-channel MOS transistor. The first transistorT11 may receive the input signal IN at its gate, may be coupled to thenode, from which the high voltage VH is provided, at its source and maybe coupled to a first output node ON1 at its drain. The first outputsignal OUT1 may be output through the first output node ON1. The secondtransistor T12 may receive the input signal IN at its gate and may becoupled to the first output node ON1 at its drain. The third transistorT13 may receive the delay control voltage VC at its gate, may be coupledat its drain to the source of the second transistor T12 and may becoupled to the node, from which the low voltage VL is provided, at itssource. The third transistor T13 may change an amount of current flowingfrom the source of the second transistor T12 to the node, from which thelow voltage VL is provided, based on the delay control voltage VC. Thefourth transistor T14 may receive the second output signal OUT2 at itsgate and may be coupled to the node, from which the low voltage VL isprovided, at its source. The fifth transistor T15 may receive the firstswitching signal SW1 at its gate, may be coupled at its drain to thesource of the second transistor T12 and may be coupled at its source tothe drain of the fourth transistor T14. The fourth transistor T14 mayfurther change the amount of current flowing from the source of thesecond transistor T12 to the node, from which the low voltage VL isprovided, based on the second output signal OUT2. The fifth transistorT15 may selectively couple the fourth transistor T14 to the source ofthe second transistor T12 based on the first switching signal SW1. Thesixth transistor T16 may receive the delay control voltage VC at itsgate and may be coupled to the node, from which the low voltage VL isprovided, at its source. The seventh transistor T17 may receive thesecond switching signal SW2 at its gate, may be coupled at its drain tothe source of the second transistor T12 and may be coupled at its sourceto the drain of the sixth transistor T16. The sixth transistor T16 mayfurther change the amount of current flowing from the source of thesecond transistor T12 to the node, from which the low voltage VL isprovided, based on the delay control voltage VC. The seventh transistorT17 may selectively couple the sixth transistor T16 to the source of thesecond transistor T12 based on the second switching signal SW2.

The third inverter 21A may include a first transistor T21 and a secondtransistor T22. The first transistor T21 may be a P-channel MOStransistor. The second transistor T22 may be a N-channel MOS transistor.The second current source 22A may include a third transistor T23. Thethird transistor T23 may be a N-channel MOS transistor. The secondfeedback current source 23A may include a fourth transistor T24 and afifth transistor T25. Each of the fourth transistor T24 and the fifthtransistor T25 may be a N-channel MOS transistor. The second auxiliarycurrent source 25A may include a sixth transistor T26 and a seventhtransistor T27. Each of the sixth transistor T26 and the seventhtransistor T27 may be a N-channel MOS transistor. The first transistorT21 may receive the first output signal OUT1 at its gate, may be coupledto the node, from which the high voltage VH is provided, at its sourceand may be coupled to a second output node ON2 at its drain. The secondoutput signal OUT2 may be output through the second output node ON2. Thesecond transistor T22 may receive the first output signal OUT1 at itsgate and may be coupled to the second output node ON2 at its drain. Thethird transistor T23 may receive the delay control voltage VC at itsgate, may be coupled at its drain to the source of the second transistorT22 and may be coupled to the node, from which the low voltage VL isprovided, at its source. The third transistor T23 may change an amountof current flowing from the source of the second transistor T22 to thenode, from which the low voltage VL is provided, based on the delaycontrol voltage VC. The fourth transistor T24 may receive at its gatethe output signal OUT3 output from the subsequent delay cell and may becoupled to the node, from which the low voltage VL is provided, at itssource. The fifth transistor T25 may receive the first switching signalSW1 at its gate, may be coupled at its drain to the source of the secondtransistor T22 and may be coupled at its source to the drain of thefourth transistor T24. The fourth transistor T24 may further change theamount of current flowing from the source of the second transistor T22to the node, from which the low voltage VL is provided, based on theoutput signal OUT3 output from the subsequent delay cell. The fifthtransistor T25 may selectively couple the fourth transistor T24 to thesource of the second transistor T22 based on the first switching signalSW1. The sixth transistor T26 may receive the delay control voltage VCat its gate and may be coupled to the node, from which the low voltageVL is provided, at its source. The seventh transistor T27 may receivethe second switching signal SW2 at its gate, may be coupled at its drainto the source of the second transistor T22 and may be coupled at itssource to the drain of the sixth transistor T26. The sixth transistorT26 may further change the amount of current flowing from the source ofthe second transistor T22 to the node, from which the low voltage VL isprovided, based on the delay control voltage VC. The seventh transistorT27 may selectively couple the sixth transistor T26 to the source of thesecond transistor T22 based on the second switching signal SW2.

Referring to FIG. 10B, the delay line 1000B may include a first delaycell 10B and a second delay cell 20B. The first delay cell 10B mayinvert an input signal IN to generate a first output signal OUT1. Thefirst delay cell 10B may inversion-drive the first output signal OUT1 tooutput a first delayed clock signal DCLK1. The second delay cell 20B mayinvert the first output signal OUT1 to generate a second output signalOUT2. The second delay cell 20B may inversion-drive the second outputsignal OUT2 to output a second delayed clock signal DCLK2. Pull-updriving force, with which the first delay cell 10B pulls up the firstoutput signal OUT1 according to the input signal IN, may change based onthe delay control voltage VC and the second output signal OUT2. Pull-updriving force, with which the second delay cell 20B pulls up the secondoutput signal OUT2 according to the first output signal OUT1, may changebased on the delay control voltage VC and an output signal OUT3 outputfrom a subsequent delay cell, which is disposed subsequently to thesecond delay cell 20B and configured to receive the second output signalOUT2. In an embodiments, a voltage level outputted from the delay cellmay be quickly changed and the delay amount of the delay cell may bedecreased as the pull-up driving force of the delay cell is increased.The voltage level outputted from the delay cell may be slowly changedand the delay amount of the delay cell may be increased as the pull-updriving force of the delay cell is decreased.

The first delay cell 10B may include a first inverter 11B, a firstcurrent source 12B and a first feedback current source 13B. The firstinverter 11B may receive the input signal IN and may invert the inputsignal IN to generate the first output signal OUT1. The first inverter11B may be coupled between a node, from which the high voltage VH isprovided, and a node, from which the high voltage VL is provided. Thefirst inverter 11B may invert the input signal IN. The first currentsource 12B may be coupled between the first inverter 11B and the node,from which the high voltage VH is provided. The first current source 12Bmay receive the delay control voltage VC. The first current source 12Bmay change the pull-up driving force of the first inverter 11B based onthe delay control voltage VC to change the delay amount of the firstdelay cell 10B. The first feedback current source 13B may be coupledbetween the first inverter 11B and the node, from which the high voltageVH is provided. The first feedback current source 13B may receive thesecond output signal OUT2. The first feedback current source 13B mayfurther change the pull-up driving force of the first inverter 11B basedon the second output signal OUT2. In an embodiment, the first feedbackcurrent source 13B may further receive a first switching signal SW1. Thefirst feedback current source 13B may be selectively coupled to thefirst inverter 11B according to the first switching signal SW1. Thefirst delay cell 10B may further include a second inverter 14B. Thesecond inverter 14B may inversion-drive the first output signal OUT1 tooutput the first delayed clock signal DCLK1.

In an embodiment, the first delay cell 10B may further include a firstauxiliary current source 15B. The first auxiliary current source 15B maybe coupled between the first inverter 11B and the node, from which thehigh voltage VH is provided. The first auxiliary current source 15B mayreceive the delay control voltage VC. The first auxiliary current source15B may further change the pull-up driving force of the first inverter11B based on the delay control voltage VC. In an embodiment, the firstauxiliary current source 15B may further receive a second switchingsignal SW2. The first auxiliary current source 15B may be selectivelycoupled to the first inverter 11B according to the second switchingsignal SW2.

The second delay cell 20B may include a third inverter 21B, a secondcurrent source 22B and a second feedback current source 23B. The thirdinverter 21B may receive the first output signal OUT1 and may invert thefirst output signal OUT1 to generate the second output signal OUT2. Thethird inverter 21B may be coupled between the node, from which the highvoltage VH is provided, and the node, from which the high voltage VL isprovided. The third inverter 21B may invert the first output signalOUT1. The second current source 22B may be coupled between the thirdinverter 21B and the node, from which the high voltage VH is provided.The second current source 22B may receive the delay control voltage VC.The second current source 22B may change the pull-up driving force ofthe third inverter 21B based on the delay control voltage VC to changethe delay amount of the second delay cell 20B. The second feedbackcurrent source 23B may be coupled between the third inverter 21B and thenode, from which the high voltage VH is provided. The second feedbackcurrent source 23B may receive the output signal OUT3 output from thesubsequent delay cell. The second feedback current source 23B mayfurther change the pull-up driving force of the third inverter 21B basedon the output signal OUT3 output from the subsequent delay cell. In anembodiment, the second feedback current source 23B may further receivethe first switching signal SW1. The second feedback current source 23Bmay be selectively coupled to the third inverter 21B according to thefirst switching signal SW1. The second delay cell 20B may furtherinclude a fourth inverter 24B. The fourth inverter 24B mayinversion-drive the second output signal OUT2 to output the seconddelayed clock signal DCLK2.

In an embodiment, the second delay cell 20B may further include a secondauxiliary current source 25B. The second auxiliary current source 25Bmay be coupled between the third inverter 21B and the node, from whichthe high voltage VH is provided. The second auxiliary current source 25Bmay receive the delay control voltage VC. The second auxiliary currentsource 25B may further change the pull-up driving force of the thirdinverter 21B based on the delay control voltage VC. In an embodiment,the second auxiliary current source 25B may further receive the secondswitching signal SW2. The second auxiliary current source 25B may beselectively coupled to the third inverter 21B according to the secondswitching signal SW2.

The first inverter 11B may include a first transistor T31 and a secondtransistor T32. The first transistor T31 may be a P-channel MOStransistor. The second transistor T32 may be a N-channel MOS transistor.The first current source 12B may include a third transistor T33. Thethird transistor T33 may be a P-channel MOS transistor. The firstfeedback current source 13B may include a fourth transistor T34 and afifth transistor T35. Each of the fourth transistor T34 and the fifthtransistor T35 may be a P-channel MOS transistor. The first auxiliarycurrent source 15B may include a sixth transistor T36 and a seventhtransistor T37. Each of the sixth transistor T36 and the seventhtransistor T37 may be a P-channel MOS transistor. The first transistorT31 may receive the input signal IN at its gate, may be coupled to thenode, from which the high voltage VH is provided, at its source and maybe coupled to a first output node ON1 at its drain. The first outputsignal OUT1 may be output through the first output node ON1. The secondtransistor T32 may receive the input signal IN at its gate and may becoupled to the first output node ON1 at its drain. The third transistorT33 may receive the delay control voltage VC at its gate, may be coupledto the node, from which the high voltage VH is provided, at its sourceand may be coupled at its drain to the source of the first transistorT31. The third transistor T33 may change an amount of current flowingfrom the node, from which the high voltage VH is provided, to the sourceof the first transistor T31 based on the delay control voltage VC. Thefourth transistor T34 may receive the second output signal OUT2 at itsgate and may be coupled to the node, from which the high voltage VH isprovided, at its source. The fifth transistor T35 may receive the firstswitching signal SW1 at its gate, may be coupled at its source to thedrain of the fourth transistor T34 and may be coupled at its drain tothe source of the first transistor T31. The fourth transistor T34 mayfurther change the amount of current flowing from the node, from whichthe high voltage VH is provided, to the source of the first transistorT31 based on the second output signal OUT2. The fifth transistor T35 mayselectively couple the fourth transistor T34 to the source of the firsttransistor T31 based on the first switching signal SW1. The sixthtransistor T36 may receive the delay control voltage VC at its gate andmay be coupled to the node, from which the high voltage VH is provided,at its source. The seventh transistor T37 may receive the secondswitching signal SW2 at its gate, may be coupled at its source to thedrain of the sixth transistor T36 and may be coupled at its drain to thesource of the first transistor T31. The sixth transistor T36 may furtherchange the amount of current flowing from the node, from which the highvoltage VH is provided, to the source of the first transistor T31 basedon the delay control voltage VC. The seventh transistor T37 mayselectively couple the sixth transistor T36 to the source of the firsttransistor T31 based on the second switching signal SW2.

The third inverter 21B may include a first transistor T41 and a secondtransistor T42. The first transistor T41 may be a P-channel MOStransistor. The second transistor T42 may be a N-channel MOS transistor.The second current source 22B may include a third transistor T43. Thethird transistor T43 may be a P-channel MOS transistor. The secondfeedback current source 23B may include a fourth transistor T44 and afifth transistor T45. Each of the fourth transistor T44 and the fifthtransistor T45 may be a P-channel MOS transistor. The second auxiliarycurrent source 25B may include a sixth transistor T46 and a seventhtransistor T47. Each of the sixth transistor T46 and the seventhtransistor T47 may be a P-channel MOS transistor. The first transistorT41 may receive the first output signal OUT1 at its gate, may be coupledto the node, from which the high voltage VH is provided, at its sourceand may be coupled to a second output node ON2 at its drain. The secondoutput signal OUT2 may be output through the second output node ON2. Thesecond transistor T42 may receive the first output signal OUT1 at itsgate and may be coupled to the second output node ON2 at its drain. Thethird transistor T43 may receive the delay control voltage VC at itsgate, may be coupled to the node, from which the high voltage VH isprovided, at its source and may be coupled at its drain to the source ofthe first transistor T41. The third transistor T43 may change an amountof current flowing from the node, from which the high voltage VH isprovided, to the source of the first transistor T41 based on the delaycontrol voltage VC. The fourth transistor T44 may receive at its gatethe output signal OUT3 output from the subsequent delay cell and may becoupled to the node, from which the high voltage VH is provided, at itssource. The fifth transistor T45 may receive the first switching signalSW1 at its gate, may be coupled at its source to the drain of the fourthtransistor T44 and may be coupled at its drain to the source of thefirst transistor T41. The fourth transistor T44 may further change theamount of current flowing from the node, from which the high voltage VHis provided, to the source of the first transistor T41 based on thesecond output signal OUT2. The fifth transistor T45 may selectivelycouple the fourth transistor T44 to the source of the first transistorT41 based on the first switching signal SW1. The sixth transistor T46may receive the delay control voltage VC at its gate and may be coupledto the node, from which the high voltage VH is provided, at its source.The seventh transistor T47 may receive the second switching signal SW2at its gate, may be coupled at its source to the drain of the sixthtransistor T46 and may be coupled at its drain to the source of thefirst transistor T41. The sixth transistor T46 may further change theamount of current flowing from the node, from which the high voltage VHis provided, to the source of the first transistor T41 based on thedelay control voltage VC. The seventh transistor T47 may selectivelycouple the sixth transistor T46 to the source of the first transistorT41 based on the second switching signal SW2.

Referring to FIG. 10C, the delay line 1000C may include a first delaycell 10C and a second delay cell 20C. The first delay cell 10C mayinvert an input signal IN to generate a first output signal OUT1. Thefirst delay cell 10C may inversion-drive the first output signal OUT1 tooutput a first delayed clock signal DCLK1. The second delay cell 20C mayinvert the first output signal OUT1 to generate a second output signalOUT2. The second delay cell 20C may inversion-drive the second outputsignal OUT2 to output a second delayed clock signal DCLK2. Pull-updriving force, with which the first delay cell 10C pulls up the firstoutput signal OUT1 according to the input signal IN, may change based ona pull-up delay control voltage VCP and the second output signal OUT2.Pull-down driving force, with which the first delay cell 10C pulls downthe first output signal OUT1 according to the input signal IN, maychange based on a pull-down delay control voltage VCN and the secondoutput signal OUT2. Pull-up driving force, with which the second delaycell 20C pulls up the second output signal OUT2 according to the firstoutput signal OUT1, may change based on the pull-up delay controlvoltage VCP and an output signal OUT3 output from a subsequent delaycell, which is disposed subsequently to the second delay cell 20C andconfigured to receive the second output signal OUT2. Pull-down drivingforce, with which the second delay cell 20C pulls down the second outputsignal OUT2 according to the first output signal OUT1, may change basedon the pull-down delay control voltage VCN and an output signal OUT3output from the subsequent delay cell. The first delay cell 10C mayinclude a first inverter 11C, a first current source 12C, a secondcurrent source 13C, a first feedback current source 14C and a secondfeedback current source 15C. The first delay cell 10C may furtherinclude a second inverter 16C, a first auxiliary current source 17C anda second auxiliary current source 18C. The second delay cell 20C mayinclude a third inverter 22C, a third current source 22C, a fourthcurrent source 23C, a third feedback current source 24C and a fourthfeedback current source 25C. The second delay cell 20C may furtherinclude a fourth inverter 26C, a third auxiliary current source 27C anda fourth auxiliary current source 28C. The delay line 1000C may beconfigured by consolidating the configurations of the delay lines 1000Aand 1000B respectively illustrated in FIGS. 10A and 10B.

The first inverter 11C may receive the input signal IN and may invertthe input signal IN to generate the first output signal OUT1. The firstcurrent source 12C may be coupled between the first inverter 11C and thenode, from which the high voltage VH is provided. The first currentsource 12C may receive the pull-up delay control voltage VCP. The firstcurrent source 12C may change the pull-up driving force of the firstinverter 11C based on the pull-up delay control voltage VCP to changethe delay amount of the first delay cell 10C. The second current source13C may be coupled between the first inverter 11C and the node, fromwhich the low voltage VL is provided. The second current source 13C mayreceive the pull-down delay control voltage VCN. The second currentsource 13C may change the pull-down driving force of the first inverter11C based on the pull-down delay control voltage VCN to change the delayamount of the first delay cell 10C. The first feedback current source14C may be coupled between the first inverter 11C and the node, fromwhich the high voltage VH is provided. The first feedback current source14C may receive the second output signal OUT2. The first feedbackcurrent source 14C may further change the pull-up driving force of thefirst inverter 11C based on the second output signal OUT2. In anembodiment, the first feedback current source 14C may further receive acomplementary signal SW1B of a first switching signal SW1. The firstfeedback current source 14C may be selectively coupled to the firstinverter 11C according to the complementary signal SW1B. The secondfeedback current source 15C may receive the second output signal OUT2.The second feedback current source 15C may be coupled between the firstinverter 11C and the node, from which the low voltage VL is provided.The second feedback current source 15C may further change the pull-downdriving force of the first inverter 11C based on the second outputsignal OUT2. In an embodiment, the second feedback current source 15Cmay further receive the first switching signal SW1. The second feedbackcurrent source 15C may be selectively coupled to the first inverter 11Caccording to the first switching signal SW1. The second inverter 16C mayinversion-drive the first output signal OUT1 to output the first delayedclock signal DCLK1. The first auxiliary current source 17C may becoupled between the first inverter 11C and the node, from which the highvoltage VH is provided. The first auxiliary current source 17C mayreceive the pull-up delay control voltage VCP. The first auxiliarycurrent source 17C may further change the pull-up driving force of thefirst inverter 11C based on the pull-up delay control voltage VCP. In anembodiment, the first auxiliary current source 17C may further receive acomplementary signal SW2B of a second switching signal SW2. The firstauxiliary current source 17C may be selectively coupled to the firstinverter 11C according to the complementary signal SW2B. The secondauxiliary current source 18C may be coupled between the first inverter11C and the node, from which the low voltage VL is provided. The secondauxiliary current source 18C may receive the pull-down delay controlvoltage VCN. The second auxiliary current source 18C may further changethe pull-down driving force of the first inverter 11C based on thepull-down delay control voltage VCN. In an embodiment, the secondauxiliary current source 18C may further receive the second switchingsignal SW2. The second auxiliary current source 18C may be selectivelycoupled to the first inverter 11C according to the second switchingsignal SW2.

The third inverter 21C may receive the first output signal OUT1 and mayinvert the first output signal OUT1 to generate the second output signalOUT2. The third current source 22C may be coupled between the secondinverter 21C and the node, from which the high voltage VH is provided.The third current source 22C may receive the pull-up delay controlvoltage VCP. The third current source 22C may change the pull-up drivingforce of the second inverter 21C based on the pull-up delay controlvoltage VCP to change the delay amount of the second delay cell 20C. Thefourth current source 23C may be coupled between the third inverter 21Cand the node, from which the low voltage VL is provided. The fourthcurrent source 23C may receive the pull-down delay control voltage VCN.The fourth current source 23C may change the pull-down driving force ofthe third inverter 21C based on the pull-down delay control voltage VCNto change the delay amount of the second delay cell 20C. The thirdfeedback current source 24C may be coupled between the third inverter21C and the node, from which the high voltage VH is provided. The thirdfeedback current source 24C may receive the output signal OUT3 outputfrom the subsequent delay cell. The third feedback current source 24Cmay further change the pull-up driving force of the third inverter 21Cbased on the output signal OUT3 output from the subsequent delay cell.In an embodiment, the third feedback current source 24C may furtherreceive the complementary signal SW1B of the first switching signal SW1.The third feedback current source 24C may be selectively coupled to thethird inverter 21C according to the complementary signal SW1B. Thefourth feedback current source 25C may receive the output signal OUT3output from the subsequent delay cell. The fourth feedback currentsource 25C may be coupled between the third inverter 21C and the node,from which the low voltage VL is provided. The fourth feedback currentsource 25C may further change the pull-down driving force of the thirdinverter 21C based on the output signal OUT3 output from the subsequentdelay cell. In an embodiment, the fourth feedback current source 25C mayfurther receive the first switching signal SW1. The fourth feedbackcurrent source 25C may be selectively coupled to the third inverter 21Caccording to the first switching signal SW1. The fourth inverter 26C mayinversion-drive the second output signal OUT2 to output the seconddelayed clock signal DCLK2. The third auxiliary current source 27C maybe coupled between the third inverter 21C and the node, from which thehigh voltage VH is provided. The third auxiliary current source 27C mayreceive the pull-up delay control voltage VCP. The third auxiliarycurrent source 27C may further change the pull-up driving force of thethird inverter 21C based on the pull-up delay control voltage VCP. In anembodiment, the third auxiliary current source 27C may further receivethe complementary signal SW2B of the second switching signal SW2. Thethird auxiliary current source 27C may be selectively coupled to thethird inverter 21C according to the complementary signal SW2B. Thefourth auxiliary current source 28C may be coupled between the thirdinverter 21C and the node, from which the low voltage VL is provided.The fourth auxiliary current source 28C may receive the pull-down delaycontrol voltage VCN. The fourth auxiliary current source 28C may furtherchange the pull-down driving force of the third inverter 21C based onthe pull-down delay control voltage VCN. In an embodiment, the fourthauxiliary current source 28C may further receive the second switchingsignal SW2. The fourth auxiliary current source 28C may be selectivelycoupled to the third inverter 21C according to the second switchingsignal SW2.

FIG. 11 is a diagram illustrating a configuration of a semiconductorapparatus 1100 in accordance with an embodiment. Referring to FIG. 11 ,the semiconductor apparatus 1100 may receive a clock signal CLK and mayperform a delay-locking operation on the clock signal CLK to generate aplurality of internal clock signals. The semiconductor apparatus 1100may include a delay locked loop circuit in order to generate theplurality of internal clock signals from the clock signal CLK. Thesemiconductor apparatus 1100 may include a clock receiver 1110, adivision circuit 1120, a first delay locked loop 1130, a second delaylocked loop 1140 and a clock generation circuit 1150. The clock receiver1110 may receive the clock signal CLK provided from an external of thesemiconductor apparatus 1100. The clock receiver 1110 may buffer theclock signal CLK to output a buffered clock signal CLKR. The divisioncircuit 1120 may receive the buffered clock signal CLKR and a frequencyinformation signal EN. The frequency information signal EN may haveinformation about whether the semiconductor apparatus 1100 operates witha relatively high frequency or with a relatively low frequency. Forexample, when the semiconductor apparatus 1100 operates with a highfrequency, the frequency information signal EN may be enabled. Forexample, when the semiconductor apparatus 1100 operates with a lowfrequency lower than the high frequency, the frequency informationsignal EN may be disabled. The division circuit 1120 may receive thebuffered clock signal CLKR and may divide the buffered clock signal CLKRto generate a divided clock signal ICLK. The division circuit 1120 mayprovide the divided clock signal ICLK as a reference clock signal. Thedivision circuit 1120 may selectively output the buffered clock signalCLKR based on the frequency information signal EN. For example, thedivision circuit 1120 may output, when the frequency information signalEN is disabled, the first delay locked loop 1130 with the divided clocksignal ICLK together with the buffered clock signal CLKR.

The first delay locked loop 1130 may be a digital delay locked loopincluding at least one digitally controlled delay line. The first delaylocked loop 1130 may receive the reference clock signal, the frequencyinformation signal EN, a first output clock signal ICLKD1 and a secondoutput clock signal ICLKD2. The first delay locked loop 1130 may performa delay-locking operation based on the reference clock signal and onesignal selected on the basis of the frequency information signal ENbetween the first output clock signal ICLKD1 and the second output clocksignal ICLKD2. The first delay locked loop 1130 may receive, as thereference clock signal, the divided clock signal ICLK generated from thedivision circuit 1120. The first delay locked loop 1130 may delay thereference clock signal to generate a first delay locked clock signalCLKDLL1. The first delay locked loop 1130 may delay the buffered clocksignal CLKR to generate a second delay locked clock signal CLKDLL2. Whenthe frequency information signal EN is enabled, the first delay lockedloop 1130 may perform a delay-locking operation based on the firstoutput clock signal ICLKD1 and the divided clock signal ICLK and maydelay the divided clock signal ICLK to generate the first delay lockedclock signal CLKDLL1. When the frequency information signal EN isdisabled, the first delay locked loop 1130 may perform a delay-lockingoperation based on the second output clock signal ICLKD2 and the dividedclock signal ICLK and may delay the buffered clock signal CLKR togenerate the second delay locked clock signal CLKDLL2.

The second delay locked loop 1140 may be an analog delay locked loopincluding a voltage-controlled delay line. The second delay locked loop1140 may receive the first delay locked clock signal CLKDLL1 to generatethe first output clock signal ICLKD1. The second delay locked loop 1140may perform a delay-locking operation on the first delay locked clocksignal CLKDLL1 based on the first delay locked clock signal CLKDLL1 andthe first output clock signal ICLKD1 to generate the first output clocksignal ICLKD1. The second delay locked loop 1140 may delay the firstdelay locked clock signal CLKDLL1 to generate a first set of pluraloutput clock signals ICLKD1, QCLKD1, IBCLKD1 and QBCLKD1. One among thefirst set of plural output clock signals ICLKD1, QCLKD1, IBCLKD1 andQBCLKD1 may be provided as the first output clock signal ICLKD1.

The clock generation circuit 1150 may receive the second delay lockedclock signal CLKDLL2. The clock generation circuit 1150 may generate thesecond output clock signal ICLKD2 based on the second delay locked clocksignal CLKDLL2. The clock generation circuit 1150 may generate, from thesecond delay locked clock signal CLKDLL2, a second set of plural outputclock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2. One among the secondset of plural output clock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2may be provided as the second output clock signal ICLKD2. The clockgeneration circuit 1150 may further receive the frequency informationsignal EN. Based on the frequency information signal EN, the clockgeneration circuit 1150 may output, as a plurality of internal clocksignals ICLKD, QCLKD, IBCLKD and QBCLKD, one between the first set ofplural output clock signals ICLKD1, QCLKD1, IBCLKD1 and QBCLKD1 and thesecond set of plural output clock signals ICLKD2, QCLKD2, IBCLKD2 andQBCLKD2. When the frequency information signal EN is enabled, the clockgeneration circuit 1150 may output the first set of plural output clocksignals ICLKD1, QCLKD1, IBCLKD1 and QBCLKD1 as the plurality of internalclock signals ICLKD, QCLKD, IBCLKD and QBCLKD. When the frequencyinformation signal EN is disabled, the clock generation circuit 1150 mayoutput the second set of plural output clock signals ICLKD2, QCLKD2,IBCLKD2 and QBCLKD2 as the plurality of internal clock signals ICLKD,QCLKD, IBCLKD and QBCLKD.

When the semiconductor apparatus 1100 operates with a high frequency,the frequency information signal EN may be enabled and a delay-lockingoperation may be performed through the first delay locked loop 1130 andthe second delay locked loop 1140. The division circuit 1120 may dividethe buffered clock signal CLKR to output the divided clock signal ICLKas the reference clock signal. The first delay locked loop 1130 mayperform a delay-locking operation based on the divided clock signal ICLKand the first output clock signal ICLKD1 to generate the first delaylocked clock signal CLKDLL1. When the delay-locking operation of thefirst delay locked loop 1130 is completed, the second delay locked loop1140 may perform a delay-locking operation on the first delay lockedclock signal CLKDLL1 provided from the first delay locked loop 1130. Thesecond delay locked loop 1140 may perform a delay-locking operation onthe first delay locked clock signal CLKDLL1 to generate the first set ofplural output clock signals ICLKD1, QCLKD1, IBCLKD1 and QBCLKD1. Theclock generation circuit 1150 may output, as the plurality of internalclock signals ICLKD, QCLKD, IBCLKD and QBCLKD, the first set of pluraloutput clock signals ICLKD1, QCLKD1, IBCLKD1 and QBCLKD1, which areoutput from the second delay locked loop 1140.

When the semiconductor apparatus 1100 operates with a low frequency, thefrequency information signal EN may be disabled and a delay-lockingoperation may be performed through the first delay locked loop 1130. Thedivision circuit 1120 may output the divided clock signal ICLK as thereference clock signal and may output the buffered clock signal CLKRtogether with the divided clock signal ICLK. The first delay locked loop1130 may perform a delay-locking operation based on the divided clocksignal ICLK and the second output clock signal ICLKD2 and may delay thebuffered clock signal CLKR to generate the second delay locked clocksignal CLKDLL2. When the delay-locking operation of the first delaylocked loop 1130 is completed, the clock generation circuit 1150 mayreceive the second delay locked clock signal CLKDLL2 from the firstdelay locked loop 1130. The clock generation circuit 1150 may generatethe second set of plural output clock signals ICLKD2, QCLKD2, IBCLKD2and QBCLKD2 based on the second delay locked clock signal CLKDLL2. Theclock generation circuit 1150 may output the second set of plural outputclock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2 as the plurality ofinternal clock signals ICLKD, QCLKD, IBCLKD and QBCLKD.

The division circuit 1120 may include a clock divider 1121 and a gatingcircuit 1122. The clock divider 1121 may receive the buffered clocksignal CLKR and may divide the buffered clock signal CLKR. For example,the clock divider 1121 may divide the buffered clock signal CLKR by twoto generate four divided clock signals. The clock divider 1121 mayoutput, as the reference clock signal, one among the four divided clocksignals. For example, the clock divider 1121 may output, as thereference clock signal, one divided clock signal ICLK, which has a phasecorresponding to a phase of the buffered clock signal CLKR among thefour divided clock signals. The gating circuit 1122 may selectivelyoutput the buffered clock signal CLKR based on the frequency informationsignal EN. The gating circuit 1122 may receive the buffered clock signalCLKR and a complementary signal ENB of the frequency information signalEN. The gating circuit 1122 may gate the buffered clock signal CLKR bythe complementary signal ENB of the frequency information signal EN. Thegating circuit 1122 may include an AND gate. When the frequencyinformation signal EN is disabled or the complementary signal ENB of thefrequency information signal EN is enabled, the gating circuit 1122 mayoutput the buffered clock signal CLKR to the first delay locked loop1130.

The first delay locked loop 1130 may include a high-frequency delay line1131, a low-frequency delay line 1132, a replica 1133, a first phasedetector 1134 and a delay controller 1135. Each of the high-frequencydelay line 1131 and the low-frequency delay line 1132 may be a digitallycontrolled delay line. The high-frequency delay line 1131 may receivethe divided clock signal ICLK, a delay control signal DC and thefrequency information signal EN. When the frequency information signalEN is enabled, the high-frequency delay line 1131 may delay the dividedclock signal ICLK based on the delay control signal DC to generate thefirst delay locked clock signal CLKDLL1. When the frequency informationsignal EN is disabled, the high-frequency delay line 1131 may bedeactivated. The low-frequency delay line 1132 may receive the bufferedclock signal CLKR and the delay control signal DC. The low-frequencydelay line 1132 may delay the buffered clock signal CLKR based on thedelay control signal DC to generate the second delay locked clock signalCLKDLL2.

The replica 1133 may receive one between the first output clock signalICLKD1 and the second output clock signal ICLKD2. When the frequencyinformation signal EN is enabled, the replica 1133 may receive the firstoutput clock signal ICLKD1 and may delay the first output clock signalICLKD1 by an amount of modelled delay time to generate a first feedbackclock signal FBCLK1. When the frequency information signal EN isdisabled, the replica 1133 may receive the second output clock signalICLKD2 and may delay the second output clock signal ICLKD2 by an amountof the modelled delay time to generate the first feedback clock signalFBCLK1. In an embodiment, the replica 1133 may be modified to receiveone among the plurality of internal clock signals ICLKD, QCLKD, IBCLKDand QBCLKD, which are output from the clock generation circuit 1150,regardless of the frequency information signal EN. For example, thereplica 1133 may be modified to receive the internal clock signal ICLKD,which has a phase corresponding to the first output clock signal ICLKD1and the second output clock signal ICLKD2 among the plurality ofinternal clock signals ICLKD, QCLKD, IBCLKD and QBCLKD.

The first phase detector 1134 may compare the phases between the dividedclock signal ICLK, which is provided as the reference clock signal, andthe first feedback clock signal FBCLK1 to generate the first phasedetection signal PD1. The delay controller 1135 may generate the delaycontrol signal DC based on the first phase detection signal PD1. Thedelay controller 1135 may increase or decrease the value of the delaycontrol signal DC according to the logic level of the first phasedetection signal PD1. The delay control signal DC may be providedcommonly to the high-frequency delay line 1131 and the low-frequencydelay line 1132. The delay amounts of the high-frequency delay line 1131and the low-frequency delay line 1132 may be set on the basis of thedelay control signal DC.

The first delay locked loop 1130 may further include a clock selector1136. The clock selector 1136 may receive the first output clock signalICLKD1, the second output clock signal ICLKD2 and the frequencyinformation signal EN. The clock selector 1136 may receive, based on thefrequency information signal EN, one between the first output clocksignal ICLKD1 and the second output clock signal ICLKD2. The clockselector 1136 may be coupled to the replica 1133. The clock signaloutput from the clock selector 1136 may be input to the replica 1133.When the frequency information signal EN is enabled, the clock selector1136 may output the first output clock signal ICLKD1 to the replica1133. When the frequency information signal EN is disabled, the clockselector 1136 may output the second output clock signal ICLKD2 to thereplica 1133.

The second delay locked loop 1140 may include a voltage-controlled delayline 1141, a calibration circuit 1142, a second phase detector 1143 anda charge pump 1144. The voltage-controlled delay line 1141 may receivethe first delay locked clock signal CLKDLL1 and a delay control voltageVC. The voltage-controlled delay line 1141 may delay the first delaylocked clock signal CLKDLL1 based on the delay control voltage VC togenerate the first output clock signal ICLKD1 and a second feedbackclock signal FBCLK2. The voltage-controlled delay line 1141 may delaythe first delay locked clock signal CLKDLL1 to generate the first set ofplural output clock signals QCLKD1, IBCLKD1 and QBCLKD1 other than thefirst output clock signal ICLKD1. The calibration circuit 1142 mayreceive the first output clock signal ICLKD1 and the second feedbackclock signal FBCLK2. The calibration circuit 1142 may detect the phasesof the first output clock signal ICLKD1 and the second feedback clocksignal FBCLK2. The calibration circuit 1142 may delay the first outputclock signal ICLKD1 to generate a delayed reference clock signal REFD.The calibration circuit 1142 may delay the second feedback clock signalFBCLK2 to generate a delayed feedback clock signal FEBD. The calibrationcircuit 1142 may compensate for a phase error between the first outputclock signal ICLKD1 and the second feedback clock signal FBCLK2, whichmay occur due to the configurations of the second delay locked loop1140. Accordingly, the second delay locked loop 1140 to perform aprecise delay-locking operation. The calibration circuit 420 illustratedin FIG. 4 may be applied as the calibration circuit 1142. The secondphase detector 1143 may receive the delayed reference clock signal REFDand the delayed feedback clock signal FEBD. The second phase detector1143 may detect the phases of the delayed reference clock signal REFDand the delayed feedback clock signal FEBD to generate a second phasedetection signal PD2. The second phase detection signal PD2 may includean up signal UP and a down signal DN. The charge pump 1144 may receivethe second phase detection signal PD2. The charge pump 1144 may generatethe delay control voltage VC based on the second phase detection signalPD2. The charge pump 1144 may raise the voltage level of the delaycontrol voltage VC based on the up signal UP and may lower the voltagelevel of the delay control voltage VC based on the down signal DN.

The clock generation circuit 1150 may include a multi-phase clockgenerator 1151 and a clock selector 1152. The multi-phase clockgenerator 1151 may receive the second delay locked clock signal CLKDLL2.The multi-phase clock generator 1151 may generate the second set ofplural output clock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2 from thesecond delay locked clock signal CLKDLL2. The multi-phase clockgenerator 1151 may divide the phase of the second delay locked clocksignal CLKDLL2 and divide the frequency of the second delay locked clocksignal CLKDLL2 to generate the second set of plural output clock signalsICLKD2, QCLKD2, IBCLKD2 and QBCLKD2 having predetermined phasedifference therebetween. Although not illustrated, the multi-phase clockgenerator 1151 may include configurations such as a phase splitter, adivider and so forth. The clock selector 1152 may receive the frequencyinformation signal EN, the first set of plural output clock signalsICLKD1, QCLKD1, IBCLKD1 and QBCLKD1 and the second set of plural outputclock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2. Based on thefrequency information signal EN, the clock selector 1152 may output, asthe plurality of internal clock signals ICLKD, QCLKD, IBCLKD and QBCLKD,one between the first set of plural output clock signals ICLKD1, QCLKD1,IBCLKD1 and QBCLKD1 and the second set of plural output clock signalsICLKD2, QCLKD2, IBCLKD2 and QBCLKD2. When the frequency informationsignal EN is enabled, the clock selector 1152 may output the first setof plural output clock signals ICLKD1, QCLKD1, IBCLKD1 and QBCLKD1 asthe plurality of internal clock signals ICLKD, QCLKD, IBCLKD and QBCLKD.When the frequency information signal EN is disabled, the clock selector1152 may output the second set of plural output clock signals ICLKD2,QCLKD2, IBCLKD2 and QBCLKD2 as the plurality of internal clock signalsICLKD, QCLKD, IBCLKD and QBCLKD.

The semiconductor apparatus 1100 may include a command receiver 1210, acommand decoder 1220, a command delay line 1230, a clock generationreplica 1240, a delay cell replica 1250, a command selector 1260 and asynchronization circuit 1270. The command receiver 1210 may receive acommand signal CMD provided from an external of the semiconductorapparatus 1100. The command signal CMD may be a control signal forcontrolling the semiconductor apparatus 1100 to perform variousoperations. The command signal CMD may include a plurality of signals ofdifferent kinds. The command decoder 1220 may decode the command signalCMD, which is provided through the command receiver 1210, to generate aninternal command signal ICMD. The command decoder 1220 may generate theinternal command signal ICMD of various kinds based on the commandsignal CMD. For example, the internal command signal ICMD may includebut may not be limited to an active command signal, a precharge commandsignal, a read command signal, a write command signal, an on-dietermination command signal, a refresh command signal and so forth. Thecommand decoder 1220 may latch the command signal CMD, which is providedthrough the command receiver 1210, based on the buffered clock signalCLKR. The command decoder 1220 may decode the latched command signal togenerate the internal command signal ICMD.

The command delay line 1230 may receive the internal command signal ICMDand the delay control signal DC. The command delay line 1230 may delaythe internal command signal ICMD based on the delay control signal DC togenerate a delayed command signal DCMD. The delay amount of the commanddelay line 1230 may be set on the basis of the delay control signal DC.The command delay line 1230 may have substantially the sameconfiguration as the high-frequency delay line 1131 and/or thelow-frequency delay line 1132. Since the command delay line 1230, thefrequency delay line 1131 and the low-frequency delay line 1132 commonlyreceive the delay control signal DC, the delay amount of the commanddelay line 1230 may set to be substantially the same as the delay amountof the high-frequency delay line 1131 and/or the delay amount of thelow-frequency delay line 1132. The internal command signal ICMD may bedelayed through the command delay line 1230 by an time as much as thedivided clock signal ICLK or the buffered clock signal CLKR is delayedthrough the high-frequency delay line 1131 or the low-frequency delayline 1132.

The clock generation replica 1240 may delay the delayed command signalDCMD to generate an additionally delayed command signal. The clockgeneration replica 1240 may be a circuit, to which the clock generationcircuit 1150 is modelled. The clock generation replica 1240 may furtherdelay the delayed command signal DCMD by a time that is taken for theclock generation circuit 1150 to generate the second set of pluraloutput clock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2. The clockgeneration circuit 1150 may generate the second set of plural outputclock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2 from the second delaylocked clock signal CLKDLL2 that is delayed through the low-frequencydelay line 1132. Therefore, the clock generation replica 1240 may delaythe delayed command signal DCMD by an time that is taken for the secondset of plural output clock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2to be generated from the second delay locked clock signal CLKDLL2thereby matching timing of the command signal output from the clockgeneration replica 1240 to the phases of the second set of plural outputclock signals ICLKD2, QCLKD2, IBCLKD2 and QBCLKD2.

The delay cell replica 1250 may be a circuit, to which at least oneamong a plurality of delay cells configuring the voltage-controlleddelay line 1141 is modelled. A number of delay cells included in thedelay cell replica 1250 may correspond to a number of delay cellsutilized to generate the first output clock signal ICLKD1 from the firstdelay locked clock signal CLKDLL1. For example, when the first delaylocked clock signal CLKDLL1 is delayed through one delay cell to begenerated as the first output clock signal ICLKD1 within thevoltage-controlled delay line 1141, the delay cell replica 1250 may beconfigured to include one delay cell. The delay cell replica 1250 mayreceive the delayed command signal DCMD and the delay control signal DCand may delay the delayed command signal DCMD based on the delay controlvoltage VC to generate the additionally delayed command signal. Thefirst delay locked clock signal CLKDLL1 delayed through thehigh-frequency delay line 1131 may be further delayed through thevoltage-controlled delay line 1141 of the second delay locked loop 1140.The delay cell replica 1250 may delay the delayed command signal DCMD byan time that is taken for the first set of plural output clock signalsICLKD1, QCLKD1, IBCLKD1 and QBCLKD1 to be generated from the first delaylocked clock signal CLKDLL1 thereby matching timing of the commandsignal output from the delay cell replica 1250 to the phases of thefirst set of plural output clock signals ICLKD1, QCLKD1, IBCLKD1 andQBCLKD1.

The command selector 1260 may receive the output signal from the clockgeneration replica 1240, the output signal from the delay cell replica1250 and the frequency information signal EN. Based on the frequencyinformation signal EN, the command selector 1260 may output, as anasynchronized command signal ASCMD, one between the output signal fromthe clock generation replica 1240 and the output signal from the delaycell replica 1250. When the frequency information signal EN is enabled,the command selector 1260 may output the output signal from the delaycell replica 1250 as the asynchronized command signal ASCMD. When thefrequency information signal EN is disabled, the command selector 1260may output the output signal from the clock generation replica 1240 asthe asynchronized command signal ASCMD.

The synchronization circuit 1270 may receive the asynchronized commandsignal ASCMD and one among the plurality of internal clock signalsICLKD, QCLKD, IBCLKD and QBCLKD. For example, the synchronizationcircuit 1270 may receive the internal clock signal ICLKD. Thesynchronization circuit 1270 may change the domain of the asynchronizedcommand signal ASCMD. The synchronization circuit 1270 may synchronizethe asynchronized command signal ASCMD to the internal clock signalICLKD to output a synchronized command signal SCMD. The synchronizationcircuit 1270 may transform the asynchronized command signal ASCMD intothe synchronized command signal SCMD, which is synchronized with theinternal clock signal ICLKD. Internal circuits of the semiconductorapparatus 1100 may utilize the synchronized command signal SCMD. In anembodiment, the synchronization circuit 1270 may be modified to generatethe synchronized command signal SCMD, which is synchronized with theinternal clock signal QCLKD.

While certain embodiments have been described above, it will beunderstood to those skilled in the art that the embodiments describedare by way of example only. Accordingly, the delay line, delay lockedloop circuit and semiconductor apparatus using the same should not belimited based on the described embodiments. Rather, the delay line,delay locked loop circuit and semiconductor apparatus using the samedescribed herein should only be limited in light of the claims thatfollow when taken in conjunction with the above description andaccompanying drawings.

What is claimed is:
 1. A delay locked loop circuit comprising: avoltage-controlled delay line configured to delay a reference clocksignal based on a delay control voltage to generate an internal clocksignal and a feedback clock signal; a calibration circuit configured todelay the internal clock signal and the feedback clock signal togenerate a delayed reference clock signal and a delayed feedback clocksignal, and to change delay amount of the internal clock signal anddelay amount of the feedback clock signal according to phases of theinternal clock signal and the feedback clock signal; a phase detectorconfigured to compare phases between the delayed reference clock signaland the delayed feedback clock signal to generate a phase detectionsignal; and a charge pump configured to generate the delay controlvoltage based on the phase detection signal.
 2. The delay locked loopcircuit of claim 1, wherein the voltage-controlled delay line delays thereference clock signal based on the delay control voltage to generate aplurality of delayed clock signals, output one among the plurality ofdelayed clock signals as the internal clock signal and outputs anotherone among the plurality of delayed clock signals as the feedback clocksignal.
 3. The delay locked loop circuit of claim 1, wherein thevoltage-controlled delay line includes at least a first delay cell and asecond delay cell, wherein the first delay cell is configured to invertan input signal to generate a first output signal and the second delaycell is configured to invert the first output signal to generate asecond output signal, and wherein driving force, with which the firstdelay cell pulls down the first output signal, is adjusted on the basisof the delay control voltage and the second output signal.
 4. The delaylocked loop circuit of claim 1, wherein the voltage-controlled delayline includes at least a first delay cell and a second delay cell,wherein the first delay cell is configured to invert an input signal togenerate a first output signal and the second delay cell is configuredto invert the first output signal to generate a second output signal,and wherein driving force, with which the first delay cell pulls up thefirst output signal, is adjusted on the basis of the delay controlvoltage and the second output signal.
 5. The delay locked loop circuitof claim 1, wherein the voltage-controlled delay line includes at leasta first delay cell and a second delay cell and the delay control voltageincludes a pull-up control voltage and a pull-down control voltage,wherein the first delay cell is configured to invert an input signal togenerate a first output signal and the second delay cell is configuredto invert the first output signal to generate a second output signal,and wherein driving force, with which the first delay cell pulls up thefirst output signal, is adjusted on the basis of the pull-up controlvoltage and the second output signal and driving force, with which thefirst delay cell pulls down the first output signal, is adjusted on thebasis of the pull-down control voltage and the second output signal. 6.The delay locked loop circuit of claim 1, wherein, when the feedbackclock signal has a lagging phase to the internal clock signal, thecalibration circuit delays the internal clock signal by a first time togenerate the delayed reference clock signal and delays the feedbackclock signal by a second time to generate the delayed feedback clocksignal, the second time being longer than the first time, and wherein,when the feedback clock signal has a leading phase to the internal clocksignal, the calibration circuit delays the internal clock signal by thesecond time to generate the delayed reference clock signal and delaysthe feedback clock signal by the first time to generate the delayedfeedback clock signal.
 7. The delay locked loop circuit of claim 1,wherein the calibration circuit includes: a timing skew detectorconfigured to detect phases of the internal clock signal and thefeedback clock signal to generate a first phase adjustment signal and asecond phase adjustment signal; a calibration signal generatorconfigured to generate a calibration signal based on the first phaseadjustment signal and the second phase adjustment signal; and a delayadjuster configured to delay the internal clock signal based on a partof the calibration signal to generate the delayed reference clock signaland delay the feedback clock signal based on a remaining part of thecalibration signal to generate the delayed feedback clock signal.
 8. Thedelay locked loop circuit of claim 7, wherein the timing skew detectordetects the phases of the internal clock signal and the feedback clocksignal to generate a first skew detection signal and a second skewdetection signal, and generates the first phase adjustment signal andthe second phase adjustment signal according to whether logic levels ofthe first skew detection signal and the second skew detection signal arekept at a same logic level for a time corresponding to at least doubleof a unit cycle.
 9. The delay locked loop circuit of claim 7, whereinthe timing skew detector includes: a skew detector configured to detectthe phases of the internal clock signal and the feedback clock signal togenerate a first skew detection signal and a second skew detectionsignal; a filter configured to generate, in synchronization with a firstclock signal, a first even signal from the first skew detection signaland a second even signal from the second skew detection signal, togenerate, in synchronization with a second clock signal having a laggingphase to the first clock signal, a first odd signal from the first skewdetection signal and a second odd signal from the second skew detectionsignal and to generate, based on the first even signal, the second evensignal, the first odd signal and the second odd signal, a first phaseinformation signal and a second phase information signal; and a phaseadjustment signal generator configured to generate the first phaseadjustment signal based on the first phase information signal and togenerate the second phase adjustment signal based on the second phaseinformation signal.
 10. The delay locked loop circuit of claim 7,wherein the delay adjuster includes: a first variable delayer, of whicha delay amount is set on the basis of the part of the calibrationsignal, configured to delay the internal clock signal to generate thedelayed reference clock signal; and a second variable delayer, of whicha delay amount is set on the basis of the remaining part of thecalibration signal, configured to delay the feedback clock signal togenerate the delayed feedback clock signal.
 11. A delay locked loopcircuit comprising: a voltage-controlled delay line configured to delaya reference clock signal based on a delay control voltage to generate aninternal clock signal and a feedback clock signal; a calibration circuitconfigured to generate a calibration signal based on the internal clocksignal and the feedback clock signal, and to delay the internal clocksignal and the feedback clock signal based on the calibration signal togenerate a delayed reference clock signal and a delayed feedback clocksignal; a phase detector configured to compare phases between thedelayed reference clock signal and the delayed feedback clock signal togenerate a phase detection signal; and a charge pump configured togenerate the delay control voltage based on the phase detection signal.12. The delay locked loop circuit of claim 11, wherein the calibrationcircuit includes: a timing skew detector configured to detect phases ofthe internal clock signal and the feedback clock signal to generate afirst phase adjustment signal and a second phase adjustment signal; acalibration signal generator configured to generate the calibrationsignal based on the first phase adjustment signal and the second phaseadjustment signal; and a delay adjuster configured to delay the internalclock signal and the feedback clock signal based on the calibrationsignal to generate the delayed reference clock signal and the delayedfeedback clock signal.
 13. The delay locked loop circuit of claim 12,wherein the delay adjuster is configured to delay the internal clocksignal based on a part of the calibration signal to generate the delayedreference clock signal and delay the feedback clock signal based on aremaining part of the calibration signal to generate the delayedfeedback clock signal.